Acquisitions and Dispositions - Narrative (Details) - USD ($) $ in Millions						3 Months Ended				6 Months Ended
	Jul. 25, 2023	Dec. 20, 2022	Oct. 17, 2022	Sep. 30, 2022	Apr. 01, 2022	Sep. 30, 2023	Jun. 30, 2023	Sep. 01, 2022	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Business Acquisition [Line Items]
Payments for acquisition of businesses, net of cash acquired										$ 0	$ 668
Goodwill							$ 37,109			37,109		$ 36,811
Tax expense							181		$ 137	305	235
Part noncash divestiture, amount of consideration received										0	$ 111
Disposal Group, Disposed of by Sale | Financial Reconciliation Business
Business Acquisition [Line Items]
Disposal group, current assets							70			70
Disposal group, current liabilities							$ 15			15
Disposal Group, Disposed of by Sale | Financial Reconciliation Business | Forecast
Business Acquisition [Line Items]
Gain (loss) on disposition of business						$ 160
Disposal Group, Disposed of by Sale | Financial Reconciliation Business | Subsequent Event
Business Acquisition [Line Items]
Net proceeds from sale of businesses and other assets	$ 230
Disposal Group, Disposed of by Sale | Fiserv Costa Rica, S.A.
Business Acquisition [Line Items]
Gain (loss) on disposition of business			$ 44							(3)
Consideration from sale of business			49
Tax expense			$ 8
Disposal Group, Disposed of by Sale | Korea Operations
Business Acquisition [Line Items]
Net proceeds from sale of businesses and other assets				$ 43
Gain (loss) on disposition of business				(127)
Consideration from sale of business				50
Part noncash divestiture, amount of consideration received				7
Disposal group, including discontinued operation, goodwill				40
Disposal group, including discontinued operation, intangible assets				48
Disposal group, including discontinued operation, accumulated foreign currency translation loss				$ 56
Merchant One, Inc.
Business Acquisition [Line Items]
Payments for acquisition of businesses, net of cash acquired		$ 302
Acquired cash		1
Increase (decrease) in goodwill										$ 61
Intangible assets		118
Goodwill		179
Other net assets		$ 6
Finxact, Inc.
Business Acquisition [Line Items]
Intangible assets					$ 105
Goodwill					670
Other net assets					1
Payments for acquisitions of businesses					$ 645
Pre-tax gain from remeasurement									$ 110
Other Acquisitions
Business Acquisition [Line Items]
Intangible assets								$ 23
Goodwill								22
Payments for acquisitions of businesses								44
Earn-out provisions estimated fair value								6
Other net assumed liabilities								(1)
Goodwill, expected tax deductible amount								$ 17