Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Trading Arrangement: Trading Arrangement [Axis] Maximum Maximum [Member] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] 4.400% senior notes due July 2049 4.4% Senior Notes Due July 2049 [Member] 4.4% Senior Notes Due July 2049 [Member] Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Title of 12(b) Security Title of 12(b) Security Carrying value Reported Value Measurement [Member] Subsequent Event Subsequent Event [Member] Weighted-Average Interest Rate Debt, Weighted Average Interest Rate Reporting Unit 1 Reporting Unit 1 [Member] Reporting Unit 1 Adjustment to Compensation, Amount Adjustment to Compensation Amount 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] 3.000% Senior Notes due 2031 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] Segment Reporting [Abstract] Segment Reporting [Abstract] Disposal group, including discontinued operation, other assets Disposal Group, Including Discontinued Operation, Other Assets Settlement anticipation cash advances, collection period Settlement Anticipation Cash Advances, Collection Period Settlement Anticipation Cash Advances, Collection Period Non-cash foreign currency exchange losses Realized Gain (Loss), Foreign Currency Transaction, before Tax Trademarks Trademarks [Member] 3.85% Senior Notes Due June 2025 3.85% Senior Notes Due June 2025 [Member] 3.85% Senior Notes Due 2025 [Member] Loss contingency accrual Loss Contingency Accrual Deferred: Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Contract assets Contract with Customer, Asset, after Allowance for Credit Loss Derivative Instrument [Axis] Derivative Instrument [Axis] Proceeds from divestiture of businesses Proceeds from Divestiture of Businesses Allowance for Merchant Credit Losses Loss Contingencies, Policy [Policy Text Block] Loss Contingencies, Policy [Policy Text Block] Deferred costs, capitalized, prepaid, and other assets disclosure Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block] Total current income tax expense (benefit) Current Income Tax Expense (Benefit) Dispositions (see Note 4) Goodwill, Divestiture 4.250% senior notes due June 2034 (Euro-denominated) 4.250% Senior Notes Due June 2034 [Member] 4.250% Senior Notes Due June 2034 Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Lending Joint Ventures Lending Joint Ventures [Member] Lending Joint Ventures [Member] Effective income tax rate reconciliation, tax expense (benefit), share-based payment arrangement, amount Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-Based Payment Arrangement, Amount Depreciation and other amortization Other Depreciation and Amortization Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Payments to acquire noncontrolling interests of consolidated subsidiaries Payments to Noncontrolling Interests Schedule of cash and cash equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Prepaid Expenses and Other Current Assets [Table] Prepaid Expenses and Other Current Assets [Table] Prepaid Expenses and Other Current Assets [Table] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share 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 Foreign Deferred Foreign Income Tax Expense (Benefit) Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Number of reportable segments Number of Reportable Segments Total current liabilities Liabilities, Current Customer relationships Customer Relationships [Member] Derivative liability, current Derivative Liability, Current Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Increase in other noncurrent assets and liabilities, net Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net Entity Address, City or Town Entity Address, City or Town Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] 5.350% senior notes due March 2031 5.350% Senior Notes Due March 2031 [Member] 5.350% Senior Notes Due March 2031 Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Product Product revenue Product [Member] Intangible assets, Net Book Value Intangible Asset, Finite-Lived, after Accumulated Amortization Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Depreciation and amortization Depreciation, Depletion and Amortization, Adjusted Depreciation, Depletion and Amortization, Adjusted Distributions from unconsolidated affiliates Proceeds from Equity Method Investment, Distribution, Return of Capital Level 2 Fair Value, Inputs, Level 2 [Member] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Total other comprehensive income (loss) Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Reporting Unit 10 Reporting Unit 10 [Member] Reporting Unit 10 Subsequent Event Type [Axis] Subsequent Event Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Schedule of segment reporting information Segment Reporting [Table Text Block] 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. Use of Estimates Use of Estimates, Policy [Policy Text Block] Related Party [Axis] Related and Nonrelated Parties [Axis] Settlement anticipation cash advances, net Payments For Settlement of Anticipation Program Payments For Settlement of Anticipation Program Document Period End Date Document Period End Date Payfare Payfare [Member] Payfare Reporting unit, percentage of fair value in excess of carrying amount Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount Debt instrument, face amount Debt Instrument, Face Amount Debt maturities (in days) Debt Instrument, Term Treasury stock, at cost, 253 million and 250 million shares, respectively Treasury Stock, Common, Value 4.550% senior notes due February 2031 4.550% Senior Notes Due February 2031 [Member] 4.550% Senior Notes Due February 2031 Cash Flow Information Cash Flow, Supplemental Disclosures [Text Block] Accumulated other comprehensive loss Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Consolidation Items [Domain] Consolidation Items [Domain] Settlement assets Settlement Assets, Current Operating lease liabilities Operating Lease, Liability, Current Banc of America Merchant Services Banc of America Merchant Services [Member] Banc of America Merchant Services [Member] Reporting Unit 6 Reporting Unit 6 [Member] Reporting Unit 6 Shares Used in Computing Net Income (Loss) Per Share Attributable to Fiserv, Inc. Earnings Per Share [Text Block] Shares used in computing net income (loss) attributable to Fiserv, Inc. per share: Earnings Per Share [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Debt instrument, covenant, debt-to-EBITDA ratio Debt Instrument, Covenant, Debt-To-EBITDA Ratio Debt Instrument, Covenant, Debt-To-EBITDA Ratio Financial Guarantee Financial Guarantee [Member] Total liabilities Liabilities Trading Symbol Trading Symbol Measurement Input, Discount Rate Measurement Input, Discount Rate [Member] Capital expenditures, including capitalized software and other intangibles Payments to Acquire Property, Plant, and Equipment Retention Restricted Stock Units Retention Restricted Stock Units [Member] Retention Restricted Stock Units StoneCastle StoneCastle [Member] StoneCastle Company Selected Measure Name Company Selected Measure Name Distributions paid to noncontrolling interests Payments of Ordinary Dividends, Noncontrolling Interest Restrictions on cash and cash equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Fair Value Measurements Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Financial Segment Financial Segment [Member] Financial Segment Credit Facility [Domain] Credit Facility [Domain] Merchant cash advances, collection period Financing Receivable, Merchant Cash Advances, Collection Period Financing Receivable, Merchant Cash Advances, Collection Period Cash flows from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Cross-currency rate swap contracts designated as net investment hedges Cross Currency Interest Rate Contract [Member] Clover Capital Clover Capital [Member] Clover Capital Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Disposal Group Name [Domain] Disposal Group Name [Domain] Settlement of derivative contracts Proceeds from Derivative Instrument, Financing Activities Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Common stock equivalents (in shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Other intangible assets, net Other Intangible Assets [Member] Award Timing Predetermined Award Timing Predetermined [Flag] Settlement Assets and Obligations Settlement Assets And Obligations, Policy [Policy Text Block] Settlement Assets And Obligations, Policy Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Share-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Derivative asset, noncurrent Derivative Asset, Noncurrent Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Goodwill, period increase Goodwill, Period Increase (Decrease) Related Party Fees Related Party Fees [Member] Related Party Fees [Member] 1.125% Senior Notes due 2027 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] 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 Concentration Risk Type [Domain] Concentration Risk Type [Domain] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] 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 Settlement activity, net Proceeds From (Payments For) Settlement Activity Proceeds From (Payments For) Settlement Activity Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Short-term and current maturities of long-term debt Long-Term Debt and Lease Obligation, Current 4.000% Senior Notes due 2036 4.0% Senior Notes Due June 2036 4.0% Senior Notes Due June 2036 [Member] 4.0% Senior Notes Due June 2036 Outstanding borrowings Long-Term Line of Credit 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 Expiration Date Trading Arrangement Expiration Date Foreign Current Foreign Tax Expense (Benefit) Hedging Relationship [Axis] Hedging Relationship [Axis] State Current State and Local Tax Expense (Benefit) Total equity Balance at beginning of period Balance at end of period Equity, Including Portion Attributable to Noncontrolling Interest Affiliated entities Affiliated Entity [Member] Stock options exercisable (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Net income (loss) attributable to Fiserv, Inc. per share: Earnings Per Share Reconciliation [Abstract] CCV Group B.V. CCV Group B.V. [Member] CCV Group B.V. Software and other intangible assets obtained under financing arrangements Financed Software and Other Intangible Asset Arrangements Financed Software and Other Intangible Asset Arrangements Cash flows from investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Related Party Transaction [Axis] Related Party Transaction [Axis] Unrecognized compensation cost Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Investments in and Advances to Affiliates [Table] Investments in and Advances to Affiliates [Table] Segments [Domain] Segments [Domain] Interest Rate Swap Interest Rate Swap [Member] Property, Equipment and Other Long-Term Assets Property, Plant, and Equipment [Policy Text Block] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Business Combination [Table] Business Combination [Table] Acquisitions, Dispositions and Other Transactions Mergers, Acquisitions and Dispositions Disclosures [Text Block] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Finance lease and other financing obligations Finance Lease, Liability And Other, Current Finance Lease, Liability And Other, Current Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Total expenses Costs and Expenses Debt instrument, interest rate Interest rate, stated percentage Debt Instrument, Interest Rate, Stated Percentage Total Fiserv, Inc. shareholders’ equity Equity, Attributable to Parent Business combination, recognized identifiable assets acquired and liabilities assumed, other noncurrent assets Business Combination, Recognized Asset Acquired, Other Asset, Noncurrent Disposal Group, Disposed of by Sale, Not Discontinued Operations Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] Assets Assets [Abstract] Insider Trading Policies and Procedures [Line Items] Goodwill, measurement period adjustment Goodwill, Measurement Period Adjustment Accounts Payable and Other Current Liabilities Accounts Payable and Accrued Liabilities Disclosure [Text Block] Gain (loss) on disposition of business, tax effect Gain (Loss) On Disposition Of Business, Tax Effect Gain (Loss) On Disposition Of Business, Tax Effect Performance Share Units Performance Shares [Member] Prepaid expenses and other current assets Total prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Deferred income taxes Total deferred income tax expense (benefit) Deferred Income Tax Expense (Benefit) Enterprise Enterprise [Member] Enterprise 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 Schedule of goodwill Goodwill [Table Text Block] Entity Central Index Key Entity Central Index Key Restricted Stock Units Restricted Stock Units And Restricted Stock Awards [Member] Restricted Stock Units And Restricted Stock Awards Additional paid-in capital Additional Paid in Capital, Common Stock Equity [Abstract] Equity [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Less: other comprehensive income attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Direct costs Direct Operating Costs Other comprehensive income (loss) before reclassifications Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Ownership [Axis] Ownership [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Schedule of Investments [Line Items] Schedule of Investments [Line Items] Investment, Name [Axis] Investment, Name [Axis] AIBMS AIBMS [Member] AIBMS Schedule of income tax provision and effective income tax rate Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Shares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] Accumulated Other Comprehensive Loss Total AOCI Attributable to Parent [Member] All Individuals All Individuals [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 Contingent consideration, noncurrent Business Combination, Contingent Consideration, Liability, Noncurrent Intangible Assets Intangible Asset [Text Block] Statement [Line Items] Statement [Line Items] Total assets Assets Repayments and sales of merchant cash advances, including Clover Capital program Repayments and Sales For Merchant Cash Advances Repayments and Sales For Merchant Cash Advances 2.250% senior notes due June 2027 2.25% Senior Notes Due June 2027 [Member] 2.25% Senior Notes Due 2027 [Member] Merchant Segment Merchant Segment [Member] Merchant Segment Operating segments Operating Segments [Member] Interest expense, net Interest Expense, Nonoperating Merchant cash advances, including Clover Capital program Payments For Merchant Cash Advances Payments For Merchant Cash Advances Equity securities without a readily determinable fair value Equity Securities without Readily Determinable Fair Value, Amount Investments in and Advances to Affiliates [Abstract] Long-term debt: Long-Term Debt, Other Disclosure [Abstract] Share-Based Compensation Share-Based Payment Arrangement [Text Block] Term Loan Facilities Term Loan Facilities [Member] Term Loan Facility [Member] PEO PEO [Member] 2.875% Senior Notes due 2028 2.875% senior notes due June 2028 (Euro-denominated) 2.875% Senior Notes Due June 2028 [Member] 2.875% Senior Notes Due June 2028 Other long-term liabilities Other Liabilities, Noncurrent Goodwill Goodwill, beginning balance Goodwill, ending balance Goodwill Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Corporate and Other Corporate Reconciling Items And Eliminations [Member] Corporate Reconciling Items And Eliminations [Member] Number of redeemable noncontrolling interests Number Of Redeemable Noncontrolling Interests Number Of Redeemable Noncontrolling Interests Retained Earnings Retained Earnings [Member] Revolving Credit Facility Revolving credit facility Revolving Credit Facility [Member] Prepaid Expenses and Other Current Assets [Line Items] Prepaid Expenses and Other Current Assets [Line Items] Prepaid Expenses and Other Current Assets [Line Items] Operating lease, impairment loss Operating Lease, Impairment Loss Cash and cash equivalents included in settlement assets Settlement Assets, Current, Cash And Cash Equivalents Settlement Assets, Current, Cash And Cash Equivalents Fair Value Measurements Fair Value Measurement, Policy [Policy Text Block] Common shares balance at beginning of period (in shares) Common shares balance at end of period (in shares) Common Stock, Shares, Outstanding Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Award Timing Disclosures [Line Items] Foreign Currency Translation Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Diluted (in dollars per share) Earnings Per Share, Diluted 4.200% senior notes due October 2028 4.2% Senior Notes Due October 2028 [Member] 4.2% Senior Notes Due 2028 [Member] Other Strategic Investments Other Strategic Investments [Member] Other Strategic Investments Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Litigation Case [Domain] Litigation Case [Domain] Amortization of intangible assets Intangible Asset, Finite-Lived, Amortization Expense Intangible Asset, Finite-Lived [Line Items] Intangible Asset, Finite-Lived [Line Items] Ownership [Domain] Ownership [Domain] First Data Subsidiary Merchant Matters First Data Subsidiary Merchant Matters [Member] First Data Subsidiary Merchant Matters [Member] Measurement Input, Terminal Growth Rate Measurement Input, Terminal Growth Rate [Member] Measurement Input, Terminal Growth Rate Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Revenue Revenue from Contract with Customer, Excluding Assessed Tax Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] 5.150% senior notes due March 2027 5.150% Senior Notes Due March 2027 [Member] 5.150% Senior Notes Due March 2027 Issuing Issuing [Member] Issuing U.S. dollar commercial paper notes U.S. Unsecured Commercial Paper Notes [Member] U.S. Unsecured Commercial Paper Notes Weighted-Average Remaining Contractual Term (Years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract] Operating income (loss) Reportable segment operating income Operating Income (Loss) Performance obligations expected to be satisfied Revenue, Remaining Performance Obligation, Amount Related Party Transaction [Domain] Related Party Transaction [Domain] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] 3.750% senior notes due October 2030 (Euro-denominated) 3.750% Senior Notes Due October 2030 [Member] 3.750% Senior Notes Due October 2030 Common stock, shares issued (in shares) Common Stock, Shares, Issued Investments in Unconsolidated Affiliates Investments in and Advances to Affiliates, Schedule of Investments [Text Block] 2.25% Senior Notes Due July 2025 2.25% Senior Notes Due July 2025 [Member] 2.25% Senior Notes Due July 2025 [Member] Accumulated Other Comprehensive Loss Comprehensive Income (Loss) Note [Text Block] Trade accounts receivable Increase (Decrease) in Accounts Receivable Product and Service [Domain] Product and Service [Domain] Class of Stock [Line Items] Class of Stock [Line Items] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] 1.625% Senior Notes due 2030 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] Deferred income taxes Deferred Income Tax Liabilities, Net Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Termination Date Trading Arrangement Termination Date Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Business combination, recognized identifiable assets acquired and liabilities assumed, finite-lived intangibles Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Finite-Lived Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Tax impacts of foreign currency translation (see Note 7) Foreign currency translation adjustment, tax Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Fair Value as of Grant Date Award Grant Date Fair Value Net gain on disposition of businesses and other assets Gain (Loss) on Disposition of Assets Schedule of Goodwill [Table] Goodwill [Table] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Arrangement Duration Trading Arrangement Duration Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name First Data Joint Venture First Data Joint Venture [Member] First Data Joint Venture [Member] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Intangible assets, Gross Carrying Amount Intangible Asset, Finite-Lived, before Accumulated Amortization Processing, administrative, and other fees Revenues Revenues Income (loss) from investments in unconsolidated affiliates (Income) loss from investments in unconsolidated affiliates Income (Loss) from Equity Method Investments Accounts payable and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount 5.600% senior notes due March 2033 5.6% Senior Notes Due March 2033 [Member] 5.6% Senior Notes Due March 2033 Share-based compensation arrangement by share-based payment award, award vesting period Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period Goodwill [Roll Forward] Goodwill [Roll Forward] Intangible Asset, Finite-Lived, Class [Domain] Intangible Asset, Finite-Lived, Class [Domain] Stock options exercisable (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted-Average Remaining Contractual Term 4.250% Senior Notes due 2034 4.25% Senior Notes Due June 2034 [Member] 4.25% Senior Notes Due June 2034 Trade names Trade Names [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] Award Type [Domain] Award Type [Domain] Level 3 Fair Value, Inputs, Level 3 [Member] Small Business Small Business [Member] Small Business Purchases of treasury stock (in shares) Treasury Stock, Shares, Acquired Foreign Merchants Foreign Merchants [Member] Foreign Merchants Ownership percentage by noncontrolling owner Subsidiary, Ownership Percentage, Noncontrolling Owner Geographical [Axis] Geographical [Axis] Restricted cash Restricted Cash Proceeds from divestiture of interest in joint venture Proceeds from Divestiture of Interest in Joint Venture Disposal group, including discontinued operation, long-term debt Disposal Group, Including Discontinued Operation, Long-Term Debt Disposal Group, Including Discontinued Operation, Long-Term Debt Contract liabilities Contract with Customer, Liability Schedule of Short-Term Debt [Table] Short-Term Debt [Table] Payments of acquisition-related contingent consideration Payment for Contingent Consideration Liability, Financing Activities Interest expense, net Interest Income (Expense), Operating and Nonoperating Foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax Legal Entity [Axis] Legal Entity [Axis] Purchases of treasury stock Treasury Stock, Value, Acquired, Cost Method Cash and cash equivalents, beginning balance Cash and cash equivalents, ending balance Total cash and cash equivalents on the consolidated statements of cash flows Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Schedule of Finite-Lived Intangible Assets [Table] Intangible Asset, Finite-Lived [Table] Accrued professional fees Accrued Professional Fees, Current Non-NEOs Non-NEOs [Member] Percentage of interest owned in affiliate Equity Method Investment, Ownership Percentage Reporting Unit [Domain] Reporting Unit [Domain] Short-term and current maturities of long-term debt: Debt, Current [Abstract] Allowance for Doubtful Accounts Credit Loss, Financial Instrument [Policy Text Block] Schedule of debt, net of discounts and debt issuance costs Schedule of Debt [Table Text Block] Debt instrument, interest rate, increase (decrease) due to credit rating below investment grade Debt Instrument, Interest Rate, Increase (Decrease) Due to Credit Rating Below Investment Grade Debt Instrument, Interest Rate, Increase (Decrease) Due to Credit Rating Below Investment Grade Investment, Name [Domain] Investment, Name [Domain] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Contract liabilities Contract with Customer, Liability, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Award Type [Axis] Award Type [Axis] Fair market value adjustment on derivatives Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Retained earnings Retained Earnings (Accumulated Deficit) Product and Service [Axis] Product and Service [Axis] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Common Stock, par value $0.01 per share Common Shares Common Stock [Member] Banking Banking [Member] Uruguay and Other Uruguay and Other [Member] Uruguay and Other 4.750% senior notes due March 2030 4.75% Senior Notes Due March 2030 [Member] 4.75% Senior Notes Due March 2030 Non-US Non-US [Member] Acquired software and technology Technology-Based Intangible Assets, Acquired [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Foreign currency translation Goodwill, Foreign Currency Translation, Gain (Loss) Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Total liabilities and equity Liabilities and Equity Employee Stock Option Share-Based Payment Arrangement, Option [Member] Noncontrolling interests Equity, Attributable to Noncontrolling Interest Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Related Party [Domain] Related and Nonrelated Parties [Domain] Tabular List, Table Tabular List [Table Text Block] Income tax receivables Income Taxes Receivable, Current Name Awards Close in Time to MNPI Disclosures, Individual Name Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Stock options outstanding Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value Preferred stock, no par value: 25 million shares authorized; none issued Preferred Stock, Value, Issued Adjustment to Compensation: Adjustment to Compensation [Axis] Amounts reclassified from accumulated other comprehensive loss Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activity Foreign currency translation gain (loss) Translation Adjustment Functional to Reporting Currency, Increase (Decrease), Gross of Tax Credit Facility [Axis] Credit Facility [Axis] Long-term debt Total long-term debt Long-Term Debt and Lease Obligation Name Measure Name Pay vs Performance Disclosure [Line Items] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Subscriber funds Fair Value Disclosure, off-Balance-Sheet Risks, Amount, Liability Debt Instrument [Line Items] Debt Instrument [Line Items] Proceeds from sale of investments Proceeds from Sale of Equity Securities, FV-NI Additional Paid-In Capital Additional Paid-in Capital [Member] Settlement obligations Settlement Liabilities, Current Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Goodwill impairment Goodwill impairment Goodwill, Impairment Loss Revenue not from contract with customer Revenue Not from Contract with Customer Name Trading Arrangement, Individual Name Cash and cash equivalents Cash and cash equivalents on the consolidated balance sheets Cash and Cash Equivalent Company Selected Measure Amount Company Selected Measure Amount Depreciation and amortization expense Depreciation, Depletion and Amortization Shares issued under stock plans (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Hardware obtained under financing arrangements Financed Hardware Agreements Financed Hardware Agreements Right-of-use assets obtained in exchange for lease liabilities - finance leases Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Non-PEO NEO Non-PEO NEO [Member] Gain (loss) in fair value of cross-currency rate swaps Gain (Loss), Foreign Currency Transaction, before Tax Net income (loss) Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Cost of goods sold and services Cost of Product and Service Sold Award Timing Method Award Timing Method [Text Block] Net change in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Interest rate cash flow hedge loss reclassified to earnings, net Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Processing Processing [Member] Processing [Member] Net income (loss) attributable to Fiserv, Inc. Net Income (Loss) Attributable to Parent Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Balance Sheet Location [Axis] Location, Statement of Financial Position, Balance [Axis] Proceeds from sale of property, plant, and equipment Proceeds from Sale of Property, Plant, and Equipment Restatement Determination Date: Restatement Determination Date [Axis] Goodwill, measurement input Goodwill, Measurement Input Goodwill, Measurement Input Changes in accumulated other comprehensive loss by component, net of income taxes Schedule of Accumulated Other Comprehensive Income (Loss) [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 Interest Expense, Net Interest Expense, Policy [Policy Text Block] Revenues: Revenues [Abstract] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Statistical Measurement [Domain] Statistical Measurement [Domain] 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. Document Fiscal Year Focus Document Fiscal Year Focus Performance obligations expected to be satisfied, expected timing Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Preferred stock, par value (in dollars per share) Preferred Stock, No Par Value Collateral held Loss Contingency, Collateral Held Loss Contingency, Collateral Held 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] Interest expense Interest Expense, Operating and Nonoperating Allowance for credit loss, current Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Current Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Other prepaid expenses Other Prepaid Expense, Current 2.650% senior notes due June 2030 2.65% Senior Notes Due June 2030 [Member] 2.65% Senior Notes Due 2030 [Member] Line of Credit Line of Credit [Member] Restatement Determination Date Restatement Determination Date Effective income tax rate reconciliation, change in deferred tax assets valuation allowance, amount Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount 5.375% senior notes due August 2028 5.375% Senior Notes Due August 2028 [Member] 5.375% Senior Notes Due August 2028 Finance lease and other financing obligations Finance Lease, Liability And Other, Noncurrent Finance Lease, Liability And Other, Noncurrent Allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss Amendment Flag Amendment Flag Goodwill [Line Items] Goodwill [Line Items] Schedule of notional amounts of outstanding derivative positions Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Loss Contingencies [Table] Loss Contingencies [Table] Capitalized software and other intangibles, Gross Carrying amount Intangible Asset, Finite-Lived, and Capitalized Cost, Software to be Sold, Leased, or Marketed, before Accumulated Amortization Equity investments Equity Method Investee [Member] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Entity Address, State or Province Entity Address, State or Province PEO Total Compensation Amount PEO Total Compensation Amount Foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Assets Assets, Fair Value Disclosure [Abstract] Capitalized expenditures, including capitalized software and other intangibles Segment Reporting, Long-Lived Asset, Expenditure for Addition Unrecognized tax benefits, increase resulting from prior period tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Derivative, notional amount Notional amount of derivatives Derivative, Notional Amount Basic (in shares) Weighted-average common shares outstanding used for the calculation of net income (loss) attributable to Fiserv, Inc. per share – basic (in shares) Weighted Average Number of Shares Outstanding, Basic Goodwill, accumulated impairment loss Goodwill, Impaired, Accumulated Impairment Loss Loss Contingencies [Line Items] Loss Contingencies [Line Items] Reporting Units Impacted By Impairment Reporting Units Impacted By Impairment [Member] Reporting Units Impacted By Impairment Schedule of supplemental cash flow information Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Merchants Utilizing Clover Capital Cash Advance Program Merchants Utilizing Clover Capital Cash Advance Program [Member] Merchants Utilizing Clover Capital Cash Advance Program Document Information [Line Items] Document Information [Line Items] Measurement Input, Long-Term Revenue Growth Rate Measurement Input, Long-Term Revenue Growth Rate [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Vested (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Class of Stock [Axis] Class of Stock [Axis] Revenue from Contract with Customer Benchmark Revenue from Contract with Customer Benchmark [Member] Intangible assets, Accumulated Amortization Intangible Asset, Finite-Lived, Accumulated Amortization Redeemable Noncontrolling Interest Redeemable Noncontrolling Interest, Policy [Policy Text Block] Redeemable Noncontrolling Interest, Policy Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity 5.600% Senior Notes Due March 2033 5.600% Senior Notes Due March 2033 [Member] 5.600% Senior Notes Due March 2033 MoneyPass Group MoneyPass Group [Member] MoneyPass Group Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Litigation Case [Axis] Litigation Case [Axis] Contract liabilities Increase (Decrease) in Contract with Customer, Liability Noncontrolling Interests Noncontrolling Interest [Member] Gain (loss) on disposition of property plant equipment Gain (Loss) on Disposition of Property Plant Equipment Reporting Unit 8 Reporting Unit 8 [Member] Reporting Unit 8 Prepaid Expenses and Other Current Assets Prepaid Expenses And Other Current Assets [Policy Text Block] Prepaid Expenses And Other Current Assets Long-term debt Long-Term Debt Proceeds from related party debt Proceeds from Related Party Debt Changes in assets and liabilities, net of effects from acquisitions and dispositions: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Unrecognized tax benefits Unrecognized Tax Benefits Contract costs Increase (Decrease) in Contract with Customer, Asset Equity Equity [Text Block] Security Exchange Name Security Exchange Name Proceeds from disposition of businesses and other assets, net of cash disposed Proceeds from Sales of Business, Affiliate and Productive Assets Increase in valuation allowance Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Transferrable federal tax credits Transferrable Federal Tax Credit Payable, Current Transferrable Federal Tax Credit Payable, Current Accrued interest Interest Payable, Current Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Name Outstanding Recovery, Individual Name Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] State Deferred State and Local Income Tax Expense (Benefit) Computation of shares used in calculating basic and diluted net income per common share Schedule of Weighted Average Number of Shares [Table Text Block] Time-Based Restricted Stock Units Time-Based Restricted Stock Units [Member] Time-Based Restricted Stock Units 5.450% senior notes due March 2028 5.45% Senior Notes Due March 2028 [Member] 5.45% Senior Notes Due March 2028 Geographical [Domain] Geographical [Domain] Schedule of interest expense, net Interest Income and Interest Expense Disclosure [Table Text Block] Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Fiserv Funding Unlimited Company Fiserv Funding Unlimited Company [Member] Fiserv Funding Unlimited Company Euro commercial paper notes Euro Unsecured Commercial Paper Notes [Member] Euro Unsecured Commercial Paper Notes Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Interest-only asset on sale of merchant cash advances Interest-Only Asset, Sale of Merchant Cash Advances Interest-Only Asset, Sale of Merchant Cash Advances Capitalized software and other intangibles, Accumulated Amortization Intangible Asset, Finite-Lived, and Capitalized Cost, Software to be Sold, Leased, or Marketed, Accumulated Amortization Other non-cash impairment charges Other Noncash Expense Proceeds from divestiture of businesses, net of cash divested Proceeds from Divestiture of Businesses, Net of Cash Divested Pension Plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Long-term debt Outstanding borrowings Long-Term Debt, Gross 5.450% senior notes due March 2034 5.450% Senior Notes Due March 2034 [Member] 5.450% Senior Notes Due March 2034 Compensation Amount Outstanding Recovery Compensation Amount Individual: Individual [Axis] Business combination, voting equity interest acquired, percentage Business Combination, Voting Equity Interest Acquired, Percentage Diluted (in shares) Weighted-average common shares outstanding used for the calculation of net income (loss) attributable to Fiserv, Inc. per share – diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Entity Emerging Growth Company Entity Emerging Growth Company Derivatives Derivatives, Policy [Policy Text Block] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Commercial Paper Commercial Paper [Member] Derivatives and Hedging Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Outstanding Borrowings Short-Term Debt Carrying value of non-contingent liability Guarantor Obligations, Current Carrying Value Revenue from Contract with Customer [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) Treasury Shares Treasury Stock, Common [Member] Income tax benefit related to goodwill impairment loss Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount Intangible Asset, Goodwill and Other [Abstract] Intangible Asset, Goodwill and Other [Abstract] 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 All Executive Categories All Executive Categories [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Reporting Unit 9 Reporting Unit 9 [Member] Reporting Unit 9 Disposal group, including discontinued operation, intangible assets Disposal Group, Including Discontinued Operation, Intangible Assets Originations of merchant cash advances, held for sale Payment for Origination, Merchant Cash Advances Held-for-Sale Payment for Origination, Merchant Cash Advances Held-for-Sale Accounting Changes and Error Corrections [Abstract] Accounting Changes and Error Corrections [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Contingent earn-out provisions Disposal Group, Including Discontinued Operation, Contingent Earn-Out Provisions, Maximum Disposal Group, Including Discontinued Operation, Contingent Earn-Out Provisions, Maximum Business Segment Information Segment Reporting [Text Block] Minimum Minimum [Member] Contingent debt guarantee Guarantees, Fair Value Disclosure Disaggregation of revenue Disaggregation of Revenue [Table Text Block] Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Stock options outstanding (in years) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted-Average Remaining Contractual Term Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Earn-out provisions estimated fair value Business Combination, Consideration Transferred, Liabilities Incurred Business Combination [Line Items] Business Combination [Line Items] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Accrued compensation and benefits Accrued Employee Benefits, Current 5.625% senior notes due August 2033 5.625% Senior Notes Due August 2033 [Member] 5.625% Senior Notes Due August 2033 Exercise Price Award Exercise Price Segment Reporting [Line Items] Segment Reporting [Line Items] Document Quarterly Report Document Quarterly Report Amortization of financing costs and debt discounts Amortization Of Debt Issuance Costs, Discounts And Other Amortization Of Debt Issuance Costs, Discounts And Other Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Income (loss) before income taxes and income (loss) from investments in unconsolidated affiliates Income (loss) before income taxes and income (loss) from investments in unconsolidated affiliates Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest 3.500% Senior Notes due 2032 3.500% senior notes due June 2032 (Euro-denominated) 3.5% Senior Notes Due June 2032 [Member] 3.5% Senior Notes Due June 2032 Unamortized discount and deferred financing costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Investments in unconsolidated affiliates Equity Method Investments Equity Component [Domain] Equity Component [Domain] Measurement Input Type [Domain] Measurement Input Type [Domain] Foreign currency forward exchange contracts Foreign Exchange Contract [Member] Adoption Date Trading Arrangement Adoption Date Proceeds from issuance of treasury stock Proceeds from Issuance or Sale of Equity Counterparty Name [Domain] Counterparty Name [Domain] Wells Fargo Merchant Services (WFMS) Wells Fargo Merchant Services (WFMS) [Member] Wells Fargo Merchant Services (WFMS) Other (expense) income Nonoperating Income (Expense) Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Accounting Policies [Abstract] Accounting Policies [Abstract] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Finite-lived intangible assets, period decrease Intangible Asset, Finite-Lived, Period Increase (Decrease) 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 Other financing activities Proceeds from (Payment for) Other Financing Activity Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Selling, general and administrative Selling, General and Administrative Expense Decrease in unrecognized tax benefits reasonably possible Decrease in Unrecognized Tax Benefits is Reasonably Possible Business Combination [Domain] Business Combination [Domain] Capital contribution from noncontrolling interest Noncontrolling Interest, Increase from Subsidiary Equity Issuance Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] 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] Common stock, $0.01 par value: 1,800 million shares authorized; 784 million shares issued Common Stock, Value, Outstanding All Adjustments to Compensation All Adjustments to Compensation [Member] Corporate and Other Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Other operating activities Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item Business Combination [Axis] Business Combination [Axis] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation 5.250% senior notes due August 2035 5.250% Senior Notes Due August 2035 [Member] 5.250% Senior Notes Due August 2035 Fiserv, Inc. Shareholders’ Equity: Equity, Attributable to Parent [Abstract] Income Statement [Abstract] Income Statement [Abstract] Purchased software Software, Purchased [Member] Document Transition Report Document Transition Report Expenses: Operating Expenses [Abstract] Prepaid maintenance, postage and insurance Prepaid Maintenance, Postage And Insurance Prepaid Maintenance, Postage And Insurance Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Schedule of intangible assets by class Intangible Asset, Finite-Lived [Table Text Block] City Area Code City Area Code Geographic Concentration Risk Geographic Concentration Risk [Member] Document Information [Table] Document Information [Table] Total debt Debt Instrument, Fair Value Disclosure Name Forgone Recovery, Individual Name Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] 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] Entity [Domain] Entity [Domain] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Accounts payable and other current liabilities Accounts Payable and Other Accrued Liabilities, Current Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Share-based compensation expense Share-Based Payment Arrangement, Expense 5.150% Senior Notes Due March 2027 and 4.400% Senior Notes Due July 2049 5.150% Senior Notes Due March 2027 and 4.400% Senior Notes Due July 2049 [Member] 5.150% Senior Notes Due March 2027 and 4.400% Senior Notes Due July 2049 Measurement Basis [Axis] Measurement Basis [Axis] Exercised (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Reporting Unit [Axis] Reporting Unit [Axis] 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 Revenue recognized which was included in the contract liability balance Contract with Customer, Liability, Revenue Recognized Subsequent Event Type [Domain] Subsequent Event Type [Domain] Payables and Accruals [Abstract] Payables and Accruals [Abstract] Accrued taxes Taxes Payable, Current 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 First Data First Data [Member] First Data [Member] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Entity Current Reporting Status Entity Current Reporting Status Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Liabilities Liabilities, Fair Value Disclosure [Abstract] Cash Flow Hedging Cash Flow Hedging [Member] Adjustments to reconcile net income (loss) to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] 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 Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Cash flows from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Property and equipment, net Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization Schedule of stockholders equity Schedule of Stockholders Equity [Table Text Block] Intangible Asset, Finite-Lived, Class [Axis] Intangible Asset, Finite-Lived, Class [Axis] Underlying Securities Award Underlying Securities Amount Fair value Estimate of Fair Value Measurement [Member] Revenue Recognition Revenue from Contract with Customer [Text Block] Total prepaid expenses Prepaid Expense, Current 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] Forfeited (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Other investing activities Payment for (Proceeds from) Other Investing Activity Segment Reporting [Table] Segment Reporting [Table] Contingent consideration, current Business Combination, Contingent Consideration, Liability, Current Total other current assets Other Assets, Current Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Other intangible assets, net Intangible Assets, Excluding Customer Relationships [Member] Intangible Assets, Excluding Customer Relationships Processing and services Processing and services revenue Processing And Services [Member] Processing And Services [Member] All Trading Arrangements All Trading Arrangements [Member] Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Tax impacts of derivatives Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Current Fiscal Year End Date Current Fiscal Year End Date Loss on disposition of business Gain (Loss) on Disposition of Business Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Cash advances Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Current Entity File Number Entity File Number Shares issued under stock plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Accrued payment network fees Accrued Payment Network Fees, Current Accrued Payment Network Fees, Current Net borrowings from commercial paper and short-term borrowings Proceeds from (Repayments of) Short-Term Debt Distributions paid to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Reclassification adjustment for net realized losses (gains) on cash flow hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax Summary of stock option activity Share-Based Payment Arrangement, Option, Activity [Table Text Block] Weighted-Average Exercise Price Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Measure: Measure [Axis] Merchant credit losses Merchant Credit Losses [Member] Merchant Credit Losses [Member] Treasury stock (in shares) Treasury shares balance at beginning of period (in shares) Treasury shares balance at end of period (in shares) Treasury Stock, Common, Shares Other operating expense Other Cost and Expense, Operating Equity Components [Axis] Equity Components [Axis] Net income taxes paid, including transferable federal tax credits Income Tax Paid, after Refund Received Reporting Unit 5 Reporting Unit 5 [Member] Reporting Unit 5 Contract costs, net Capitalized Contract Cost, Net Entity Interactive Data Current Entity Interactive Data Current Less: net income attributable to noncontrolling interests Less: net income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Total Accounts Payable and Accrued Liabilities, Current Change in estimated redemption value of redeemable noncontrolling interest (see Note 11) Noncontrolling Interest, Change in Redemption Value Entity Small Business Entity Small Business Comprehensive income (loss) attributable to Fiserv, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Acquired finite-lived intangible assets, weighted average useful life Intangible Asset, Finite-Lived, Acquired, Weighted-Average Amortization Period Student Loan Servicing Business Student Loan Servicing Business [Member] Student Loan Servicing Business Net gain on early debt extinguishment Gain (Loss) on Extinguishment of Debt, Net of Adjustments Gain (Loss) on Extinguishment of Debt, Net of Adjustments MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Other long-term assets Other Assets, Noncurrent Document Type Document Type Payments for acquisition of businesses, net of cash acquired Cash flows from investing activities Payments to Acquire Businesses, Net of Cash Acquired 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] Gain on early debt extinguishment Gain (Loss) on Extinguishment of Debt Brazil BRAZIL Stock options exercisable Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value Other current assets Other Assets, Miscellaneous, Current Debt proceeds Proceeds from Issuance of Long-Term Debt Local Phone Number Local Phone Number Long-term contract liabilities Contract with Customer, Liability, Noncurrent Net Investment Hedging Net Investment Hedging [Member] Commitments and Contingencies (see Note 17) Commitments and Contingencies 3.500% senior notes due July 2029 3.5% Senior Notes Due July 2029 [Member] 3.5% Senior Notes Due July 2029 [Member] 5.150% senior notes due August 2034 5.15% Senior Notes Due August 2034 [Member] 5.15% Senior Notes Due August 2034 Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Executive Category: Executive Category [Axis] Argentina ARGENTINA Counterparty Name [Axis] Counterparty Name [Axis] Liabilities and Equity Liabilities and Equity [Abstract] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Reporting Unit 7 Reporting Unit 7 [Member] Reporting Unit 7 PEO Name PEO Name Derivatives Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Cash acquired from acquisition Cash Acquired from Acquisition Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Derivative Instruments and Hedging Activities Disclosures [Table] Derivative Instruments and Hedging Activities Disclosures [Table] Exercised (in dollars per share) Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Revenue Recognition Revenue [Policy Text Block] Other accrued expenses Other Accrued Liabilities, Current Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Ownership percentage in disposed asset Disposal Group, Including Discontinued Operation, Ownership Percentage in Disposed Asset Disposal Group, Including Discontinued Operation, Ownership Percentage in Disposed Asset Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument [Axis] Debt Instrument [Axis] Net assumed liabilities Business Combination, Recognized Liability Assumed, Other Liability, Noncurrent Share-based compensation Share-Based Payment Arrangement, Noncash Expense Personnel expenses Labor and Related Expense Disposal Group Name [Axis] Disposal Group Name [Axis] Digital Payments Digital Payments [Member] Digital Payments Basic (in dollars per share) Earnings Per Share, Basic Measurement Input Type [Axis] Measurement Input Type [Axis] Total current assets Assets, Current Insider Trading Arrangements [Line Items] Debt repayments, including redemption and other costs Repayment of Long-Term Debt, Long-Term Lease Obligation, and Capital Security Pinch Payments, Money Money Acquisitions, and CardFree Pinch Payments, Money Money Acquisitions, and CardFree [Member] Pinch Payments, Money Money Acquisitions, and CardFree Payments of debt financing costs Payments of Financing Costs Trade accounts receivable, less allowance for doubtful accounts Accounts Receivable, after Allowance for Credit Loss, Current 3.200% senior notes due July 2026 3.2% Senior Notes Due July 2026 [Member] 3.2% Senior Notes Due July 2026 [Member] Schedule of short-term debt Schedule of Short-Term Debt [Table Text Block] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Cover [Abstract] Equity securities without readily determinable fair value, upward price adjustment, annual amount Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount Percentage of concentration risk Concentration Risk, Percentage Foreign lines of credit Foreign Line of Credit [Member] Equity Awards Adjustments Equity Awards Adjustments [Member] Hedging Relationship [Domain] Hedging Relationship [Domain] Derivative liability, noncurrent Derivative Liability, Noncurrent Reporting Unit 3 Reporting Unit 3 [Member] Reporting Unit 3 Total short-term and current maturities of long-term debt Debt, Current Aggregate merchant credit loss expense Loss Contingency Accrual, Loss (Reversal of Loss) MoneyPass Network, ATM Managed Services and Cash Intelligence Business MoneyPass Network, ATM Managed Services and Cash Intelligence Business [Member] MoneyPass Network, ATM Managed Services and Cash Intelligence Business Other expense, net Other Nonoperating Income (Expense) Debt Long-Term Debt [Text Block] Repayments of senior debt Repayments of Senior Debt Foreign currency-denominated debt Foreign Currency-Denominated Debt [Member] Foreign Currency-Denominated Debt Fair value hedge accounting adjustments (see Note 8) Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease) Schedule of accounts payable and accrued expenses Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Purchases of investments Payments to Acquire Investments ICICI Merchant Services Private Limited ICICI Merchant Services Private Limited [Member] ICICI Merchant Services Private Limited Forfeited (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Reporting Unit 4 Reporting Unit 4 [Member] Reporting Unit 4 Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Class of Stock [Domain] Class of Stock [Domain] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Acquisition of noncontrolling interest of consolidated subsidiary Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Foreign exchange forward contracts Foreign Exchange Forward [Member] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Income Taxes Income Tax Disclosure [Text Block] Trade accounts payable Accounts Payable, Current 4.500% Senior Notes due 2031 4.500% senior notes due May 2031 (Euro-denominated) 4.500% Senior Notes Due May 2031 [Member] 4.500% Senior Notes Due May 2031 Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Business combination, consideration transferred Business Combination, Consideration Transferred Entity Filer Category Entity Filer Category Supplemental Cash Flow Elements [Abstract] Supplemental Cash Flow Elements [Abstract] Proceeds from repayments and sales of merchant cash advances, originally classified as held for sale Proceeds From Repayments And Sales Of Merchant Cash Advances Proceeds From Repayments And Sales Of Merchant Cash Advances Reporting Unit 2 Reporting Unit 2 [Member] Reporting Unit 2 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] Client deposits Contract With Customer, Liability, Customer Deposits, Current Contract With Customer, Liability, Customer Deposits, Current Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Distributions from unconsolidated affiliates Proceeds from Equity Method Investment, Distribution Schedule of Stock by Class [Table] Stock, Class of Stock [Table] Net income (loss) Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest 3.750% Senior Notes due 2030 3.75% Senior Notes Due June 2030 [Member] 3.75% Senior Notes Due June 2030 Senior Notes Senior Notes [Member] Foreign Currency Foreign Currency Transactions and Translations Policy [Policy Text Block] Entity Address, Address Line One Entity Address, Address Line One Right-of-use assets obtained in exchange for lease liabilities - operating leases Right-of-Use Asset Obtained in Exchange for Operating Lease Liability 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 Income tax provision Income tax provision Income Tax Expense (Benefit) Proceeds from repayments and sales of merchant cash advances, originally classified as held for sale Proceeds From Repayments And Sales Of Merchant Cash Advances, Originally Classified as Held-For-Sale Proceeds From Repayments And Sales Of Merchant Cash Advances, Originally Classified as Held-For-Sale Fair Value Hedging Fair Value Hedging [Member] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Principles of Consolidation Consolidation, Policy [Policy Text Block] Recent Accounting Pronouncements Accounting Standards Update and Change in Accounting Principle [Text Block] Intangible assets, net Capitalized software and other intangibles, Net Book Value Intangible Asset, Finite-Lived, and Capitalized Cost, Software to be Sold, Leased, or Marketed, after Accumulated Amortization Disposal group, including discontinued operation, goodwill Disposal Group, Including Discontinued Operation, Goodwill Statement [Table] Statement [Table] Treasury Lock Treasury Lock [Member] Interest income Investment Income, Interest Schedule of remaining performance obligations Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block] Derivative Instruments and Hedging Activities Disclosures [Line Items] Derivative Instruments and Hedging Activities Disclosures [Line Items] Contract with customer, asset and liabilities Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Federal Current Federal Tax Expense (Benefit) Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Fixed-To-Floating Interest Rate Swap Fixed-To-Floating Interest Rate Swap [Member] Fixed-To-Floating Interest Rate Swap Derivative Instruments and Hedging Activities Disclosure [Abstract]