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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 5.450% senior notes due March 2034 5.450% Senior Notes Due March 2034 [Member] 5.450% Senior Notes Due March 2034 Deferred income taxes Deferred Income Tax Expense (Benefit) Document Information [Line Items] Document Information [Line Items] Statement of Comprehensive Income 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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] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] 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] Subsidiary 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