Equity (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Accounting Standards Update [Extensible List]			Accounting Standards Update 2016-13
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	$ 33,070	$ 34,595
Net income (loss)	308	368
Measurement period adjustments related to First Data acquisition		(122)
Distributions paid to noncontrolling interests		(14)
Other comprehensive income (loss)	(158)	(643)
Share-based compensation	66	108
Shares issued under stock plans	(88)	(75)
Purchases of treasury stock	(612)	(885)
Balance at end of period	32,586	33,287	$ 34,595
Net income attributable to redeemable noncontrolling interest	10	9
Distributions paid to redeemable noncontrolling interests	$ 10	$ 12
Common Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period (in shares)	789	791
Balance at beginning of period	$ 8	$ 8
Balance at end of period (in shares)	789	791	791
Balance at end of period	$ 8	$ 8	$ 8
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period (in shares)	121	112
Balance at beginning of period	$ (4,375)	$ (3,118)
Shares issued under stock plans (in shares)	(3)	(3)
Shares issued under stock plans	$ 99	$ 81
Purchases of treasury stock (in shares)	5	8
Purchases of treasury stock	$ (612)	$ (885)
Balance at end of period (in shares)	123	117	112
Balance at end of period	$ (4,888)	$ (3,922)	$ (3,118)
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	23,643	23,741
Share-based compensation	66	108
Shares issued under stock plans	(187)	(156)
Balance at end of period	23,522	23,693	23,741
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(387)	(180)
Other comprehensive income (loss)	(149)	(631)
Balance at end of period	(536)	(811)	(180)
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	13,441	12,528
Net income (loss)	304	392
Balance at end of period	13,745	12,875	12,528
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	740	1,616
Net income (loss)	4	(24)
Measurement period adjustments related to First Data acquisition		(122)
Distributions paid to noncontrolling interests		(14)
Other comprehensive income (loss)	(9)	(12)
Balance at end of period	$ 735	1,444	1,616
Cumulative Effect, Period of Adoption, Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period		(45)
Balance at end of period			(45)
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period		$ (45)
Balance at end of period			$ (45)