Consolidated Statement of Changes in Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjusted Balance	Revision of Prior Period, Accounting Standards Update, Adjustment	Common stock and paid-in capital	Common stock and paid-in capital Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Deficit Revision of Prior Period, Accounting Standards Update, Adjustment	Accumulated other comprehensive (loss) income	Accumulated other comprehensive (loss) income Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated other comprehensive (loss) income Revision of Prior Period, Accounting Standards Update, Adjustment	Treasury stock	Treasury stock Cumulative Effect, Period of Adoption, Adjusted Balance
Common stock dividends, amount per share	$ 0.56
Equity at Dec. 31, 2017	$ 13,494	$ 13,375		$ 21,245	$ 21,245	$ (6,406)	$ (6,510)		$ (235)	$ (250)		$ (1,110)	$ (1,110)
Equity (Accounting Standards Update 2014-09) at Dec. 31, 2017			$ (126)					$ (126)
Equity (Accounting Standards Update 2016-01) at Dec. 31, 2017			7					(20)			$ 27
Equity (Accounting Standards Update 2018-02) at Dec. 31, 2017			0					42			(42)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,263					1,263
Share-based compensation	100			100
Other comprehensive loss (income)	(289)								(289)
Common stock repurchases	(939)											(939)
Common stock dividends	(242)					(242)
Equity at Dec. 31, 2018	$ 13,268	13,266		21,345	21,345	(5,489)	(5,499)		(539)	(531)		(2,049)	(2,049)
Equity (Accounting Standards Update 2017-08) at Dec. 31, 2018			(2)					(10)			$ 8
Common stock dividends, amount per share	$ 0.68
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 1,715					1,715
Share-based compensation	93			93
Other comprehensive loss (income)	654								654
Common stock repurchases	(1,039)											(1,039)
Common stock dividends	(273)					(273)
Equity at Dec. 31, 2019	$ 14,416	$ 13,399		21,438	$ 21,438	(4,057)	$ (5,074)		123	$ 123		(3,088)	$ (3,088)
Equity (Accounting Standards Update 2016-13) at Dec. 31, 2019			$ (1,017)					$ (1,017)
Common stock dividends, amount per share	$ 0.76
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 1,085					1,085
Share-based compensation	106			106
Other comprehensive loss (income)	508								508
Common stock repurchases	(106)											(106)
Common stock dividends	(289)					(289)
Equity at Dec. 31, 2020	$ 14,703			$ 21,544		$ (4,278)			$ 631			$ (3,194)