Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Revenue		$ 10,187	$ 5,823	$ 5,696
Expenses:
Selling, general and administrative		3,284	1,228	1,150
Gain on sale of businesses		(15)	(227)	(10)
Total expenses		8,578	4,070	4,164
Operating income		1,609	1,753	1,532
Interest expense, net		(473)	(189)	(175)
Debt financing activities		(47)	(14)	0
Other (expense) income		(6)	5	1
Income from continuing operations before income taxes and income from investments in unconsolidated affiliates		1,083	1,555	1,358
Income tax provision		(198)	(378)	(158)
Income from investments in unconsolidated affiliates		29	10	32
Income from continuing operations		914	1,187	1,232
Income from discontinued operations, net of income taxes		0	0	14
Net income		914	1,187	1,246
Less: Net income attributable to noncontrolling interests and redeemable noncontrolling interests		21	0	0
Net income attributable to Fiserv, Inc.		$ 893	$ 1,187	$ 1,246
Net income attributable to Fiserv, Inc. per share - basic:
Continuing operations (in dollars per share)		$ 1.74	$ 2.93	$ 2.92
Discontinued operations (in dollars per share)		0	0	0.03
Total (in dollars per share)		1.74	2.93	2.95
Net income attributable to Fiserv, Inc. per share - diluted:
Continuing operations (in dollars per share)		1.71	2.87	2.86
Discontinued operations (in dollars per share)		0	0	0.03
Total (in dollars per share)		$ 1.71	$ 2.87	$ 2.89
Shares used in computing net income attributable to Fiserv, Inc. per share:
Basic (in shares)		512.3	405.5	422.3
Diluted (in shares)		522.6	413.7	431.3
Equity investments | Related Party Fees
Shares used in computing net income attributable to Fiserv, Inc. per share:
Processing, administrative service, and other fees		$ 112	$ 28	$ 0
Processing and services
Revenue:
Revenue	[1]	8,573	4,975	4,833
Expenses:
Cost of goods and services sold		4,016	2,324	2,291
Product
Revenue:
Revenue		1,614	848	863
Expenses:
Cost of goods and services sold		$ 1,293	$ 745	$ 733

[1] Includes processing and other fees charged to related party investments accounted for under the equity method of $112 million, $28 million and $0 million for the years ended December 31, 2019, 2018 and 2017, respectively (see Notes 9 and 20).