Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Variable Rate [Domain] Variable Rate [Domain] Corporate and Other Corporate Reconciling Items And Eliminations [Member] Corporate Reconciling Items And Eliminations [Member] Less: net income attributable to noncontrolling interests and redeemable noncontrolling interests Less: net income attributable to noncontrolling interests and redeemable noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Pay vs Performance Disclosure [Line Items] Sagent Sagent [Member] Sagent Other long-term liabilities Other Noncurrent Liabilities [Member] Statistical Measurement [Domain] Statistical Measurement [Domain] Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Changes in assets and liabilities, net of effects from acquisitions and dispositions: Increase (Decrease) in Operating Capital [Abstract] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Related Party Transaction [Line Items] Related Party Transaction [Line Items] Cash Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Award Type [Domain] Award Type [Domain] Fair Value as of Grant Date Award Grant Date Fair Value Investment, Name [Domain] Investment, Name [Domain] Performance obligations expected to be satisfied, expected timing Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Balance at beginning of period (in shares) Balance at end of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number Allowance for Doubtful Accounts Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block] Line of credit facility, interest rate at period end Line of Credit Facility, Interest Rate at Period End Schedule of purchase price allocation Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Cross-currency rate swap contracts Cross Currency Interest Rate Contract [Member] Revolving Credit Facility Revolving credit facility Revolving Credit Facility [Member] Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations Deferred income taxes Deferred Income Tax Liabilities, Net MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Performance Share Units Performance Shares [Member] Trade accounts payable Accounts Payable, Current Segment Reporting [Abstract] Segment Reporting [Abstract] Stock options exercisable (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Prepaid expenses and other current assets Prepaid Expenses and Other Current Assets [Member] Restatement Determination Date: Restatement Determination Date [Axis] Investment, Name [Axis] Investment, Name [Axis] Tax impacts of foreign currency translation Foreign currency translation adjustment, tax Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Purchases of investments Payments to Acquire Investments Other (expense) income Nonoperating Income (Expense) Commitments and Contingencies (see Note 18) Commitments and Contingencies Insider Trading Policies and Procedures [Line Items] Stock options exercisable (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Proceeds from issuance of treasury stock Proceeds from Issuance or Sale of Equity Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Equity Equity [Text Block] First Data Joint Venture First Data Joint Venture [Member] First Data Joint Venture [Member] Geographical [Axis] Geographical [Axis] Settlement obligations Settlement Liabilities, Current Income Taxes Income Tax Disclosure [Text Block] Contract liabilities Increase (Decrease) in Contract with Customer, Liability Ownership [Axis] Ownership [Axis] Other restricted cash Restricted Cash and Cash Equivalents, Noncurrent Director Director [Member] 3.500% senior notes due July 2029 3.5% Senior Notes Due July 2029 [Member] 3.5% Senior Notes Due July 2029 [Member] Revenue Recognition Revenue [Policy Text Block] Noncontrolling Interest [Abstract] Noncontrolling Interest [Abstract] Noncontrolling Interest [Table] Noncontrolling Interest [Table] Schedule of gross carrying amount and weighted-average useful life allocated to intangible assets Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block] Accumulated impairment loss Goodwill, Impaired, Accumulated Impairment Loss Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Preferred stock, no par value: 25 million shares authorized; none issued Preferred Stock, Value, Issued Business Acquisition [Line Items] Business Acquisition [Line Items] Shares (In thousands) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Net proceeds from sale of businesses and other assets Proceeds from Divestiture of Businesses Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Payments of acquisition-related contingent consideration Payment for Contingent Consideration Liability, Financing Activities Pre-tax gain from remeasurement Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain Diluted (in dollars per share) Earnings Per Share, Diluted PEO Total Compensation Amount PEO Total Compensation Amount Hedging Relationship [Axis] Hedging Relationship [Axis] Trade accounts receivable, less allowance for doubtful accounts Amounts due from unconsolidated merchant alliances Accounts Receivable, after Allowance for Credit Loss, Current Cross-currency rate swap contract Foreign Currency Contracts, Liability, Fair Value Disclosure Supplemental Cash Flow Elements [Abstract] Supplemental Cash Flow Elements [Abstract] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Level 3 Fair Value, Inputs, Level 3 [Member] 0.375% senior notes due July 2023 (Euro-denominated) 0.375% Senior Notes Due July 2023 [Member] 0.375% Senior Notes Due July 2023 [Member] Treasury stock (in shares) Balance at beginning of period (in shares) Balance at end of period (in shares) Treasury Stock, Common, Shares Line of Credit Line of Credit [Member] Stock options outstanding - balance at beginning of period (in shares) Stock options outstanding - balance at end of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number Accrued compensation and benefits Accrued Employee Benefits, Current 3.200% senior notes due July 2026 3.2% Senior Notes Due July 2026 [Member] 3.2% Senior Notes Due July 2026 [Member] Litigation Case [Axis] Litigation Case [Axis] Redeemable Noncontrolling Interests Balance at beginning of period Balance at end of period Redeemable Noncontrolling Interest, Equity, Carrying Amount Trading Symbol Trading Symbol Settlement Assets and Obligations Settlement Assets And Obligations, Policy [Policy Text Block] Settlement Assets And Obligations, Policy Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Granted (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Net income attributable to Fiserv, Inc. Net Income (Loss) Attributable to Parent Net Income (Loss) Indian Rupee India, Rupees Acquired cash Cash Acquired from Acquisition Total current liabilities Liabilities, Current Derivative Contract [Domain] Derivative Contract [Domain] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Output Solutions postage Output Solutions Postage [Member] Output Solutions Postage [Member] Foreign Currency Foreign Currency Transactions and Translations Policy [Policy Text Block] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Company Selected Measure Name Company Selected Measure Name Schedule of cash and cash equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Accrued interest Interest Payable, Current All Currencies [Domain] All Currencies [Domain] Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Liabilities and Equity Liabilities and Equity [Abstract] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Reclassification adjustment for accumulated foreign currency translation impacts from the sale of foreign entities included in net (gain) loss on sale of businesses and other assets Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax Fiserv, Inc. Shareholders’ Equity: Equity, Attributable to Parent [Abstract] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Exercised (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Contract liabilities Contract with Customer, Liability Fair market value adjustment on derivatives Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax First Data Subsidiary Merchant Matters First Data Subsidiary Merchant Matters [Member] First Data Subsidiary Merchant Matters [Member] Other intangible assets, net Other Intangible Assets [Member] Cost of goods sold and services Cost of Goods and Services Sold Executive Category: Executive Category [Axis] Weighted-Average Useful Life Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life Foreign currency forward exchange contracts Foreign Exchange Contract [Member] Computation of shares used in calculating basic and diluted net income per common share Schedule of Weighted Average Number of Shares [Table Text Block] Weighted-Average Grant Date Fair Value Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Exercised (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Name Measure Name Name Forgone Recovery, Individual Name Carrying value Reported Value Measurement [Member] United Kingdom, Pounds United Kingdom, Pounds Goodwill Goodwill Equity Components [Axis] Equity Components [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Hedging Relationship [Domain] Hedging Relationship [Domain] Measurement Basis [Axis] Measurement Basis [Axis] Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross Underlying Securities Award Underlying Securities Amount Entity Small Business Entity Small Business Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Local Phone Number Local Phone Number Trade accounts receivable Increase (Decrease) in Accounts Receivable Fair Value Measurement [Domain] Fair Value Measurement [Domain] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] ValueAct Capital Master Fund, L.P. ValueAct Capital Master Fund, L.P. [Member] ValueAct Capital Master Fund, L.P. Derivative, notional amount Derivative, Notional Amount 2.250% senior notes due July 2025 (British Pound-denominated) 2.25% Senior Notes Due July 2025 [Member] 2.25% Senior Notes Due July 2025 [Member] Settlement activity, net Proceeds From (Payments For) Settlement Activity Proceeds From (Payments For) Settlement Activity Short-term and current maturities of long-term debt: Debt, Current [Abstract] Measurement Frequency [Axis] Measurement Frequency [Axis] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Capitalized software and other intangibles Capitalized Software Development Costs [Member] Internally developed software for sale, licensing or long-term internal use (classified as intangible assets). Equity investments Equity Method Investee [Member] Debt maturities (in days) Debt Instrument, Term Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Income Statement Location [Axis] Income Statement Location [Axis] Unamortized discount and deferred financing costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax Common stock equivalents (in shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Foreign Banks and Alliance Partners Foreign Banks And Alliance Partners [Member] Foreign Banks And Alliance Partners Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Payables and Accruals [Abstract] Payables and Accruals [Abstract] Revenue Processing, administrative, and other fees Revenues Schedule of accounts payable and accrued expenses Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Product and Service [Domain] Product and Service [Domain] Other Performance Measure, Amount Other Performance Measure, Amount Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Other Equity Investments Equity Securities without Readily Determinable Fair Value [Policy Text Block] Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Amortization of acquisition-related intangible assets Amortization Of Acquisition-Related Intangible Assets The aggregate expense charged against earnings to allocate the cost of acquired intangible assets. As a noncash expense, this element is added back to net income when calculating cash provided by (used in) operations using the indirect method. Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Client deposits Contract With Customer, Liability, Customer Deposits, Current Contract With Customer, Liability, Customer Deposits, Current Stock options excluded from the calculation of diluted weighted-average outstanding shares because their impact was anti-dilutive (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Award Type [Axis] Award Type [Axis] Derivative Instruments and Hedging Activities Disclosure [Abstract] Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Document Quarterly Report Document Quarterly Report Interest expense Interest Expense Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Euro commercial paper notes Euro Unsecured Commercial Paper Notes [Member] Euro Unsecured Commercial Paper Notes Right-of-use assets obtained in exchange for lease liabilities - operating leases Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Stock options outstanding (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Trading Arrangement: Trading Arrangement [Axis] Related Party Transactions Related Party Transactions Disclosure [Text Block] Schedule of interest expense, net Interest Income and Interest Expense Disclosure [Table Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Schedule of income tax provision and effective income tax rate Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Aggregate merchant credit loss expense Loss Contingency, Loss in Period Entity File Number Entity File Number Loss Contingencies [Table] Loss Contingencies [Table] Disposal group, including discontinued operation, trade receivable and capitalized software Disposal Group, Including Discontinued Operation, Trade Receivable And Capitalized Software Disposal Group, Including Discontinued Operation, Trade Receivable And Capitalized Software Operating lease liabilities Operating Lease, Liability, Current Prepaid expenses Prepaid Expense, Current 3.800% senior notes due October 2023 3.8% Senior Notes Due October 2023 [Member] 3.8% Senior Notes Due 2023 [Member] Purchased software Computer Software, Intangible Asset [Member] Software obtained under financing arrangements Financed Software Arrangements Financed Software Arrangements Argentina ARGENTINA Amortization expense Amortization of Intangible Assets Entity Shell Company Entity Shell Company U.S. dollar commercial paper notes U.S. Unsecured Commercial Paper Notes [Member] U.S. Unsecured Commercial Paper Notes Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Singapore, Dollars Singapore, Dollars Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Intangible assets, net Net Book Value Finite-Lived Intangible Assets, Net Restatement Determination Date Restatement Determination Date Shares acquired, average cost per share (in dollars per share) Shares Acquired, Average Cost Per Share Variable-Rate Revolving Credit Facilities Due April 2027 Variable-Rate Revolving Credit Facilities Due April 2027 [Member] Variable-Rate Revolving Credit Facilities Due March 2023 [Member] Counterparty Name [Domain] Counterparty Name [Domain] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents, beginning balance Cash and cash equivalents, ending balance Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Total debt Debt Instrument, Fair Value Disclosure Interest income Investment Income, Interest Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Disposal group, including discontinued operation, intangible assets Disposal Group, Including Discontinued Operation, Intangible Assets Common stock, shares issued (in shares) Common Stock, Shares, Issued Vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Payments for acquisitions of businesses Business Combination, Consideration Transferred Contract liabilities Contract with Customer, Liability, Current Short-term and current maturities of long-term debt Long-Term Debt and Lease Obligation, Current Treasury stock, at cost, 182 million and 154 million shares, respectively Treasury stock, common, value Treasury Stock, Common, Value Security Exchange Name Security Exchange Name Long-term debt Long-Term Debt Selling, general and administrative Selling, General and Administrative Expense Accumulated other comprehensive loss Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Other comprehensive income (loss) before reclassifications Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Employee Stock Option Employee Stock Option [Member] Restricted Stock Units and Awards Restricted Stock Units And Restricted Stock Awards [Member] Restricted Stock Units And Restricted Stock Awards Foreign Currency Translation Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Derivatives and Hedging Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Schedule of amortization expense of intangible assets Finite-Lived Intangible Assets Amortization Expense [Table Text Block] Term Loan Facilities Term Loan Facilities [Member] Term Loan Facility [Member] Weighted-average period unrecognized compensation cost will be recognized (in years) Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Redeemable Noncontrolling Interests Noncontrolling Interest Disclosure [Text Block] Total expenses Costs and Expenses Other financing activities Proceeds from (Payments for) Other Financing Activities Maximum Maximum [Member] Comprehensive income (loss) attributable to Fiserv, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Merchant credit losses Merchant Credit Losses [Member] Merchant Credit Losses [Member] Unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Document Type Document Type Geographic Concentration Risk Geographic Concentration Risk [Member] Tabular List, Table Tabular List [Table Text Block] Entity Address, Address Line One Entity Address, Address Line One Purchases of treasury stock Treasury Stock, Value, Acquired, Cost Method Other Other [Member] Other Number of redeemable noncontrolling interests Number Of Redeemable Noncontrolling Interests Number Of Redeemable Noncontrolling Interests Share-Based Compensation Share-Based Payment Arrangement [Text Block] 4.500% senior notes due May 2031 (Euro-denominated) 4.500% Senior Notes Due May 2031 [Member] 4.500% Senior Notes Due May 2031 Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Contract costs, net Capitalized Contract Cost, Net Weighted-Average Exercise Price Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Accrued taxes Taxes Payable, Current Business Acquisition [Axis] Business Acquisition [Axis] Net income attributable to redeemable noncontrolling interest Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Amortization of financing costs and debt discounts Amortization Of Debt Issuance Costs, Discounts And Other Amortization Of Debt Issuance Costs, Discounts And Other Schedule of intangible assets by class Schedule of Finite-Lived Intangible Assets [Table Text Block] Variable Rate [Axis] Variable Rate [Axis] Accounts payable and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Income Statement [Abstract] Income Statement [Abstract] 2.750% senior notes due July 2024 2.75% Senior Notes Due July 2024 [Member] 2.75% Senior Notes Due July 2024 [Member] Contract costs Increase (Decrease) in Contract with Customer, Asset Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period Title of 12(b) Security Title of 12(b) Security Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Less: other comprehensive loss attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Related Party [Domain] Related Party, Type [Domain] Distributions paid to noncontrolling interests and redeemable noncontrolling interests Payments of Ordinary Dividends, Noncontrolling Interest Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Ownership percentage by noncontrolling owner Subsidiary, Ownership Percentage, Noncontrolling Owner Operating segments Operating Segments [Member] Balance at beginning of period (in dollars per share) Balance at end of period (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Shares issued under stock plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Other current assets Other Assets, Current Class of Stock [Line Items] Class of Stock [Line Items] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Payment to acquire noncontrolling interest of consolidated subsidiary Payments to Noncontrolling Interests Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Investments in and Advances to Affiliates [Table] Investments in and Advances to Affiliates [Table] Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Entity Tax Identification Number Entity Tax Identification Number Investments in unconsolidated affiliates Equity Method Investments Unrealized gain (loss) on defined benefit pension plans Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax Statistical Measurement [Axis] Statistical Measurement [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Entity Interactive Data Current Entity Interactive Data Current Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Debt Long-Term Debt [Text Block] Other net assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets 3.850% senior notes due June 2025 3.85% Senior Notes Due June 2025 [Member] 3.85% Senior Notes Due 2025 [Member] Total Shareholder Return Amount Total Shareholder Return Amount Product Product revenue Product [Member] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Acquisitions and Dispositions Mergers, Acquisitions and Dispositions Disclosures [Text Block] Segments [Domain] Segments [Domain] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Schedule of stockholders equity Schedule of Stockholders Equity [Table Text Block] Pre-tax gain Deconsolidation, Gain (Loss), Amount Consolidation Items [Domain] Consolidation Items [Domain] Retained earnings Retained Earnings (Accumulated Deficit) Measure: Measure [Axis] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Name Outstanding Recovery, Individual Name Debt instrument, face amount Debt Instrument, Face Amount Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code 3.000% Senior Notes due 2031 Three Point Zero Percent Senior Notes Due 2031 [Member] Three Point Zero Percent Senior Notes Due 2031 Part noncash divestiture, amount of consideration received Distribution of nonmonetary assets (see Note 11) Noncash or Part Noncash Divestiture, Amount of Consideration Received Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Entity Address, State or Province Entity Address, State or Province Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Counterparty Name [Axis] Counterparty Name [Axis] Disposal group, including discontinued operation, goodwill Disposal Group, Including Discontinued Operation, Goodwill Derivatives Derivatives, Policy [Policy Text Block] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Balance at beginning of period (in shares) Balance at end of period (in shares) Common Stock, Shares, Outstanding Fiserv Costa Rica, S.A. Fiserv Costa Rica, S.A. [Member] Fiserv Costa Rica, S.A. Disposal Group Name [Domain] Disposal Group Name [Domain] Other Acquisitions Series of Individually Immaterial Business Acquisitions [Member] PEO PEO [Member] Estimated range of exposure Loss Contingency, Estimate of Possible Loss Acquisition of noncontrolling interest of consolidated subsidiary Increase (Decrease) From Acquisition Of Noncontrolling Interest Of Consolidated Subsidiary Increase (Decrease) From Acquisition Of Noncontrolling Interest Of Consolidated Subsidiary Other operating activities Other Operating Activities, Cash Flow Statement AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Class of Stock [Domain] Class of Stock [Domain] Reclassification adjustment for net realized (gains) losses on cash flow hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Debt Instrument [Axis] Debt Instrument [Axis] Related Party Fees Related Party Fees [Member] Related Party Fees [Member] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Contingent debt guarantee Guarantees, Fair Value Disclosure Capital contribution from noncontrolling interest Noncontrolling Interest, Increase from Subsidiary Equity Issuance Credit Facility [Axis] Credit Facility [Axis] Korea Operations Korea Operations [Member] Korea Operations Total liabilities Liabilities Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Consideration from sale of business Disposal Group, Including Discontinued Operation, Consideration Accumulated Other Comprehensive Loss Total AOCI Attributable to Parent [Member] Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Brazil BRAZIL Long-term debt: Long-Term Debt, Other Disclosure [Abstract] Measurement Frequency [Domain] Measurement Frequency [Domain] All Executive Categories All Executive Categories [Member] Long-term contract liabilities Contract with Customer, Liability, Noncurrent Forward exchange contracts designated as cash flow hedges Cash Flow Hedge Derivative Instrument Assets at Fair Value Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Financial Guarantee Financial Guarantee [Member] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Pension Plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accounts Payable and Accrued Expenses Accounts Payable and Accrued Liabilities Disclosure [Text Block] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Related Party Transaction [Domain] Related Party Transaction [Domain] Disposal Group, Disposed of by Sale Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] Shares used in computing net income attributable to Fiserv, Inc. per share: Earnings Per Share [Abstract] Allowance for credit loss, current Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Current Cash and cash equivalents Cash and cash equivalents on the consolidated balance sheets Cash and Cash Equivalents, at Carrying Value, Including Discontinued Operations Affiliated entities Affiliated Entity [Member] Decrease in unrecognized tax benefits reasonably possible Decrease in Unrecognized Tax Benefits is Reasonably Possible Treasury Lock Treasury Lock [Member] Finance lease and other financing obligations Finance Lease, Liability And Other, Current Finance Lease, Liability And Other, Current Trade names Trade Names [Member] Accrued professional fees Accrued Professional Fees, Current Residual buyouts Residual Buyout Intangible Assets [Member] Residual Buyout Intangible Assets Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Senior Notes Senior Notes [Member] Total current assets Assets, Current Schedule of short-term debt Schedule of Short-Term Debt [Table Text Block] 5.375% senior notes due August 2028 5.375% Senior Notes Due August 2028 [Member] 5.375% Senior Notes Due August 2028 Revenue from Contract with Customer [Abstract] All Individuals All Individuals [Member] Litigation Case [Domain] Litigation Case [Domain] Other expense, net Other Nonoperating Income (Expense) Entity Filer Category Entity Filer Category Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Statement [Table] Statement [Table] Contingent consideration Business Combination, Contingent Consideration, Liability, Noncurrent Current Fiscal Year End Date Current Fiscal Year End Date 2.250% Senior Notes due 2025 Senior Notes Due 2025 [Member] Senior Notes Due 2025 [Member] Stock repurchase program, authorized amount (in shares) Stock Repurchase Program, Authorized Amount Derivative Instruments and Hedging Activities Disclosures [Line Items] Derivative Instruments and Hedging Activities Disclosures [Line Items] Recent Accounting Pronouncements Accounting Standards Update and Change in Accounting Principle [Text Block] Unrecognized tax benefits Unrecognized Tax Benefits PEO Name PEO Name 1.125% senior notes due July 2027 (Euro-denominated) 1.125% Senior Notes Due July 2027 [Member] 1.125% Senior Notes Due July 2027 [Member] Percentage of concentration risk Concentration Risk, Percentage Net proceeds from sale of businesses and other assets Proceeds from Sales of Assets, Investing Activities Changes in accumulated other comprehensive loss by component, net of income taxes Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Granted (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value 2.250% senior notes due June 2027 2.25% Senior Notes Due June 2027 [Member] 2.25% Senior Notes Due 2027 [Member] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Stock options exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value Purchases of treasury stock, including employee shares withheld for tax obligations Payments For Repurchase Of Common Stock And Payments Related To Tax Withholding For Share Based Compensation The cash outflow to reacquire common stock during the period and to satisfy an employee's income tax withholding obligation as part of a net-share settlement of a share-based award. Contingent consideration Business Combination, Contingent Consideration, Liability, Current Class of Stock [Axis] Class of Stock [Axis] Estimate of gains (losses) related to foreign currency exchange contracts during the next 12 months Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Other accrued expenses Other Accrued Liabilities, Current Finxact, Inc. Finxact, Inc. [Member] Finxact, Inc. Debt instrument, interest rate Interest rate, stated percentage Debt Instrument, Interest Rate, Stated Percentage Euro Member Countries, Euro Euro Member Countries, Euro Accounts payable and accrued expenses Total Accounts Payable and Accrued Liabilities, Current Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Gain (loss) on disposition of business Gain (Loss) on Disposition of Business Receivable, before allowance for credit loss, current Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Current Business Combination and Asset Acquisition [Abstract] Total Fiserv, Inc. shareholders’ equity Equity, Attributable to Parent Commercial Paper Commercial Paper [Member] Total purchase price Business Combination, Consideration Transferred, Including Equity Interest in Acquiree Held Prior to Combination Consolidation Items [Axis] Consolidation Items [Axis] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Share of income Temporary Equity, Net Income Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] European Merchant Services B.V. European Merchant Services B.V. [Member] European Merchant Services B.V. Revenue recognized which was included in the contract liability balance Contract with Customer, Liability, Revenue Recognized Foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Derivatives Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Summary of restricted stock and performance activity Schedule Of Share-Based Compensation, Restricted Stock Units, Restricted Stock Awards, Performance Share Units And Performance Share Awards Activity [Table Text Block] Schedule Of Share-Based Compensation, Restricted Stock Units, Restricted Stock Awards, Performance Share Units And Performance Share Awards Activity [Table Text Block] Long-term debt Total long-term debt Long-Term Debt and Lease Obligation Acquired software and technology Acquired Software And Technology [Member] Purchased software applications and internally developed software for sale, licensing or long-term internal use acquired in a business combination. Equity securities without a readily determinable fair value Equity Securities without Readily Determinable Fair Value, Amount Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table] Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table] Fair Value Measurements Fair Value Measurement, Policy [Policy Text Block] Foreign lines of credit Foreign Line of Credit [Member] Net income attributable to Fiserv, Inc. per share: Earnings Per Share Reconciliation [Abstract] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Level 2 Fair Value, Inputs, Level 2 [Member] Net Investment Hedging Net Investment Hedging [Member] Entity Emerging Growth Company Entity Emerging Growth Company Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Robert W. Hau [Member] Robert W. Hau Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities [Member] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Finance lease and other financing obligations Finance Lease, Liability And Other, Noncurrent Finance Lease, Liability And Other, Noncurrent Intangible assets Gross Carrying Amount Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Document Fiscal Period Focus Document Fiscal Period Focus Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Title Trading Arrangement, Individual Title Stock options outstanding - balance at beginning of period (in dollars per shares) Stock options outstanding - balance at end of period (in dollars per shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price Share-based compensation Share-Based Payment Arrangement, Noncash Expense Common Stock, par value $0.01 per share Common Shares Common Stock [Member] Individual: Individual [Axis] City Area Code City Area Code Entity Address, Postal Zip Code Entity Address, Postal Zip Code Shares Used in Computing Net Income Per Share Attributable to Fiserv, Inc. Earnings Per Share [Text Block] Product and Service [Axis] Product and Service [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Software maintenance Software Maintenance [Member] Software Maintenance [Member] Document Fiscal Year Focus Document Fiscal Year Focus Weighted-Average Interest Rate Debt, Weighted Average Interest Rate 3.000% senior notes due July 2031 (British Pound-denominated) 3.0% Senior Notes Due July 2031 [Member] 3.0% Senior Notes Due July 2031 [Member] Geographical [Domain] Geographical [Domain] Total equity Balance at beginning of period Balance at end of period Equity, Including Portion Attributable to Noncontrolling Interest Distributions paid to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Investments in and Advances to Affiliates [Abstract] Payments Payments Segment [Member] Payments Segment Minimum Minimum [Member] Property and equipment, net Property, Plant and Equipment, Net Distributions from unconsolidated affiliates Proceeds from Equity Method Investment, Distribution Summary of stock option activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Exercise Price Award Exercise Price Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Total other comprehensive income (loss) Other comprehensive loss Other Comprehensive Income (Loss), Net of Tax Disposal Group Classification [Axis] Disposal Group Classification [Axis] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Assets Assets [Abstract] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Debt proceeds Proceeds from Issuance of Long-Term Debt Other Product and Service, Other [Member] Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Income taxes paid Income Taxes Paid, Net Distributions paid to redeemable noncontrolling interests Distributions paid to redeemable noncontrolling interests Noncontrolling Interest, Decrease From Distributions To Redeemable Noncontrolling Interest Holders Noncontrolling Interest, Decrease From Distributions To Redeemable Noncontrolling Interest Holders Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities 4.400% senior notes due July 2049 4.4% Senior Notes Due July 2049 [Member] 4.4% Senior Notes Due July 2049 [Member] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Other investing activities Payments for (Proceeds from) Other Investing Activities Percentage of business acquired Business Acquisition, Percentage of Voting Interests Acquired Retained Earnings Retained Earnings [Member] Goodwill, expected tax deductible amount Business Acquisition, Goodwill, Expected Tax Deductible Amount Foreign currency-denominated debt Foreign Currency-Denominated Debt [Member] Foreign Currency-Denominated Debt Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Total liabilities and equity Liabilities and Equity Investments in Unconsolidated Affiliates Investments in and Advances to Affiliates, Schedule of Investments [Text Block] Other long-term assets Other Assets, Noncurrent Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Ownership [Domain] Ownership [Domain] GST/HST Law Change Goods And Services Tax / Harmonized Sales Tax Law Change [Member] Goods And Services Tax / Harmonized Sales Tax Law Change Basic (in dollars per share) Earnings Per Share, Basic Interest expense, net Interest Revenue (Expense), Net Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Accounting Policies [Abstract] Accounting Policies [Abstract] Cash and cash equivalents included in settlement assets Settlement Assets, Current, Cash And Cash Equivalents Settlement Assets, Current, Cash And Cash Equivalents Settlement assets Settlement Assets, Current Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Net (gain) loss on sale of businesses and other assets Gain (Loss) on Disposition of Assets Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Currency [Axis] Currency [Axis] Treasury stock purchases settled after the balance sheet date Treasury Stock Purchases Settled After Balance Sheet Date Treasury Stock Purchases Settled After Balance Sheet Date Arrangement Duration Trading Arrangement Duration Entity Address, City or Town Entity Address, City or Town Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Restrictions on cash and cash equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Schedule of segment reporting information Schedule of Segment Reporting Information, by Segment [Table Text Block] Less: Fair value of previously held equity interest Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value Principles of Consolidation Consolidation, Policy [Policy Text Block] Investments in and Advances to Affiliates [Line Items] Investments in and Advances to Affiliates [Line Items] Aggregate Intrinsic Value (In millions) Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Aggregate Intrinsic Value [Abstract] Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Aggregate Intrinsic Value Document Transition Report Document Transition Report Award Timing Predetermined Award Timing Predetermined [Flag] Increase (decrease) in goodwill Goodwill, Purchase Accounting Adjustments Interest Expense Interest Expense [Member] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Derecognition of redeemable noncontrolling interest Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Derivative Instruments and Hedging Activities Disclosures [Table] Derivative Instruments and Hedging Activities Disclosures [Table] Acquired software and technology Technology-Based Intangible Assets [Member] Termination Date Trading Arrangement Termination Date Common stock, shares authorized (in shares) Common Stock, Shares Authorized Depreciation and other amortization Other Depreciation and Amortization Tax impacts of derivatives Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Document Information [Table] Document Information [Table] Fintech Fintech Segment [Member] Fintech Segment [Member] Outstanding Borrowings Short-Term Debt Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Processing and services Processing and services revenue Processing And Services [Member] Processing And Services [Member] Schedule of net investment hedges in accumulated other comprehensive income (loss) Schedule of Net Investment Hedges in Accumulated Other Comprehensive Income (Loss) [Table Text Block] Merchant One, Inc. Merchant One, Inc. [Member] Merchant One, Inc. Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Derivative Instrument [Axis] Derivative Instrument [Axis] Long-term debt Outstanding borrowings Long-Term Debt, Gross 5.450% senior notes due March 2028 5.45% Senior Notes Due March 2028 [Member] 5.45% Senior Notes Due March 2028 Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Related Party Transactions [Abstract] Related Party Transactions [Abstract] All Trading Arrangements All Trading Arrangements [Member] Line of credit facility, borrowing capacity increase Line Of Credit Facility, Borrowing Capacity Increase Line Of Credit Facility, Borrowing Capacity Increase Estimated interest expense related to settled interest rate hedge contracts during the next twelve months Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net All Adjustments to Compensation All Adjustments to Compensation [Member] Common stock, $0.01 par value: 1,800 million shares authorized; 784 million shares issued Common Stock, Value, Outstanding Award Timing Disclosures [Line Items] Compensation Amount Outstanding Recovery Compensation Amount 5.600% senior notes due March 2033 5.6% Senior Notes Due March 2033 [Member] 5.6% Senior Notes Due March 2033 Schedule of remaining performance obligations Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block] Net income (loss) Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Forfeited (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Deferred income taxes Deferred Income Tax Expense (Benefit) Document Information [Line Items] Document Information [Line Items] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Earn-out provisions estimated fair value Business Combination, Consideration Transferred, Liabilities Incurred Accrued payment network fees Accrued Payment Network Fees, Current Accrued Payment Network Fees, Current Allowance for Merchant Credit Losses Loss Contingencies, Policy [Policy Text Block] Loss Contingencies, Policy [Policy Text Block] Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Cash Flow Information Cash Flow, Supplemental Disclosures [Text Block] Forfeited (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Total short-term and current maturities of long-term debt Debt, Current Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Insider Trading Arrangements [Line Items] Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss Distributions from unconsolidated affiliates Proceeds from Equity Method Investment, Distribution, Return of Capital 1.625% senior notes due July 2030 (Euro-denominated) 1.625% Senior Notes Due July 2030 [Member] 1.625% Senior Notes Due July 2030 [Member] Processing Processing [Member] Processing [Member] Related Party [Axis] Related Party, Type [Axis] Stock options outstanding Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Shares issued under stock plans (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Accounting Changes and Error Corrections [Abstract] Accounting Changes and Error Corrections [Abstract] Entity Registrant Name Entity Registrant Name Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Award Timing Method Award Timing Method [Text Block] Adjustment to Compensation, Amount Adjustment to Compensation Amount Noncontrolling interests Equity, Attributable to Noncontrolling Interest Certificado de Deposito Interbancario (CDI) Certificado De Deposito Interbancario (CDI) [Member] Certificado De Deposito Interbancario (CDI) Debt repayments Repayment of Long-Term Debt, Long-Term Lease Obligation, and Capital Security Net (repayments of) proceeds from commercial paper and short-term borrowings Proceeds from (Repayments of) Short-Term Debt Document Period End Date Document Period End Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Adoption Date Trading Arrangement Adoption Date Foreign currency translation loss Translation Adjustment Functional to Reporting Currency, Increase (Decrease), Gross of Tax Disposal Group Name [Axis] Disposal Group Name [Axis] Revenue from Contract with Customer Benchmark Revenue from Contract with Customer Benchmark [Member] Schedule of fair value, assets and liabilities measured on recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Stock options exercisable (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price Treasury Stock Treasury Stock, Common [Member] Entity Central Index Key Entity Central Index Key 4.500% Senior Notes Due 2031 Four Point Five Percent Senior Notes Due 2031 [Member] Four Point Five Percent Senior Notes Due 2031 Collateral held Loss Contingency, Collateral Held Loss Contingency, Collateral Held Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Loss contingency accrual Loss Contingency Accrual Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Share-based compensation expense Share-Based Payment Arrangement, Expense Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Gross Carrying Amount Finite-Lived Intangible Assets, Gross Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Income tax provision Tax expense Income tax provision Income Tax Expense (Benefit) Non-US Non-US [Member] Merchants Utilizing Clover Capital Cash Advance Program Merchants Utilizing Clover Capital Cash Advance Program [Member] Merchants Utilizing Clover Capital Cash Advance Program Payments of debt financing costs Payments of Financing Costs 1.625% Senior Notes due 2030 Senior Notes Due 2030 [Member] Senior Notes Due 2030 [Member] Name Trading Arrangement, Individual Name Amounts reclassified from accumulated other comprehensive loss Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Disaggregation of revenue Disaggregation of Revenue [Table Text Block] Tax impacts of defined benefit pension plans Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax Equity [Abstract] Equity [Abstract] Total consideration Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net Entity [Domain] Entity [Domain] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Amendment Flag Amendment Flag Schedule of redeemable noncontrolling interests activity Redeemable Noncontrolling Interest [Table Text Block] Intangible Assets Intangible Assets Disclosure [Text Block] Legal Entity [Axis] Legal Entity [Axis] Customer relationships, net Customer relationships Customer-Related Intangible Assets [Member] Fair Value Hedging Fair Value Hedging [Member] Other net assumed liabilities Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Other Net Assumed Liabilities Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Other Net Assumed Liabilities Payments for acquisition of businesses, net of cash acquired Payments for acquisition of businesses, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activities Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Interest expense, net Interest Income (Expense), Net Credit Facility [Domain] Credit Facility [Domain] Purchases of treasury stock (in shares) Treasury Stock, Shares, Acquired Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Diluted (in shares) Weighted-average common shares outstanding used for the calculation of net income attributable to Fiserv, Inc. per share – diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted 2.650% senior notes due June 2030 2.65% Senior Notes Due June 2030 [Member] 2.65% Senior Notes Due 2030 [Member] License and termination fees License And Termination Fees [Member] License And Termination Fees [Member] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Variable-Rate Term Loan Facilities Due April 2027 Variable-Rate Term Loan Facilities Due April 2027 [Member] Variable-Rate Term Loan Facilities Due March 2023 [Member] Contract with customer, asset and liabilities Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Right-of-use assets obtained in exchange for lease liabilities - finance leases Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Disposal group, including discontinued operation, accumulated foreign currency translation loss Disposal Group, Including Discontinued Operation, Accumulated Foreign Currency Translation Loss Disposal Group, Including Discontinued Operation, Accumulated Foreign Currency Translation Loss Suzan Kereere [Member] Suzan Kereere Subscriber funds Fair Value Disclosure, off-Balance-Sheet Risks, Amount, Liability Revenue Recognition Revenue from Contract with Customer [Text Block] Capital expenditures, including capitalized software and other intangibles Payments to Acquire Property, Plant, and Equipment Company Selected Measure Amount Company Selected Measure Amount Additional paid-in capital Additional Paid in Capital, Common Stock Additional Paid-In Capital Additional Paid-in Capital [Member] 5.625% senior notes due August 2033 5.625% Senior Notes Due August 2033 [Member] 5.625% Senior Notes Due August 2033 Proceeds from sale of investments Proceeds from Sale of Equity Securities, FV-NI Forward exchange contracts designated as cash flow hedges Cash Flow Hedge Derivative Instrument Liabilities at Fair Value Balance Sheet Location [Axis] Balance Sheet Location [Axis] Hardware, print and card production Hardware, Print, And Card Production [Member] Hardware, Print, And Card Production [Member] Total cash and cash equivalents on the consolidated statements of cash flows Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Total assets Assets Name Awards Close in Time to MNPI Disclosures, Individual Name (Loss) income from investments in unconsolidated affiliates Loss (income) from investments in unconsolidated affiliates Income (Loss) from Equity Method Investments Loss Contingencies [Line Items] Loss Contingencies [Line Items] Cover [Abstract] Cover [Abstract] Lending Joint Ventures Lending Joint Ventures [Member] Lending Joint Ventures [Member] Share-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Professional services Professional Services [Member] Professional Services [Member] Fair Value, Recurring Fair Value, Recurring [Member] Fair Value Measurements Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Uruguay URUGUAY Acceptance Acceptance Segment [Member] Acceptance Segment [Member] Other long-term liabilities Other Liabilities, Noncurrent Vested (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Non-NEOs Non-NEOs [Member] Schedule of supplemental cash flow information Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Performance obligations expected to be satisfied Revenue, Remaining Performance Obligation, Amount Interest Expense, Net Interest Expense, Policy [Policy Text Block] Business Segment Information Segment Reporting Disclosure [Text Block] First Data First Data [Member] First Data [Member] Net change in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Income before income taxes and (loss) income from investments in unconsolidated affiliates Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Non-PEO NEO Non-PEO NEO [Member] Equity Component [Domain] Equity Component [Domain] Adjustment to Compensation: Adjustment to Compensation [Axis] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Debt Instrument [Line Items] Debt Instrument [Line Items] Contract assets Contract with Customer, Asset, after Allowance for Credit Loss Basic (in shares) Weighted-average common shares outstanding used for the calculation of net income attributable to Fiserv, Inc. per share – basic (in shares) Weighted Average Number of Shares Outstanding, Basic Entity Current Reporting Status Entity Current Reporting Status 4.200% senior notes due October 2028 4.2% Senior Notes Due October 2028 [Member] 4.2% Senior Notes Due 2028 [Member] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Operating income Operating income (loss) Operating Income (Loss) Schedule of Short-Term Debt [Table] Schedule of Short-Term Debt [Table] Cost of Services Cost Of Services [Member] Cost Of Services [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Term loan facility Term Loan Facility [Member] Term Loan Facility [Member] Financial Reconciliation Business Financial Reconciliation Business [Member] Financial Reconciliation Business 1.125% Senior Notes due 2027 Senior Notes Due 2027 [Member] Senior Notes Due 2027 [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Segments [Axis] Segments [Axis] Statement [Line Items] Statement [Line Items] Fair value Estimate of Fair Value Measurement [Member] Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Weighted-Average Remaining Contractual Term (Years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Schedule of debt, net of discounts and debt issuance costs Schedule of Debt [Table Text Block] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Carrying value of non-contingent liability Guarantor Obligations, Current Carrying Value Noncontrolling Interests Noncontrolling Interest [Member]