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Related Party Transactions (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
	May 03, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	May 04, 2021	May 02, 2021	Dec. 31, 2020
Equity investments
Related Party Transaction [Line Items]
Amounts due from unconsolidated merchant alliances		$ 38		$ 38				$ 37
Related Party Fees \| Equity investments
Related Party Transaction [Line Items]
Processing, administrative, and other fees		46	$ 62	160	$ 174
New Omaha
Related Party Transaction [Line Items]
Number of shares to be repurchased (in shares)	5.0
Share repurchase amount	$ 588
New Omaha \| Fiserv
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owner						9.00%	13.00%
Merchant Alliances \| Related Party Fees \| Equity investments
Related Party Transaction [Line Items]
Processing, administrative, and other fees		42	47	132	134
Lending Solutions Business, Investment Services Business, and InvestCloud Holdings \| Related Party Fees \| Affiliated entities
Related Party Transaction [Line Items]
Processing, administrative, and other fees		$ 6	$ 16	$ 32	$ 43
Fiserv \| New Omaha
Related Party Transaction [Line Items]
Secondary public offering (in shares)	23.0