Condensed 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity	$ 13,268	$ 13,266		$ 21,345	$ 21,345	$ (5,489)	$ (5,499)		$ (539)	$ (531)		$ (2,049)	$ (2,049)
Equity | Accounting Standards Update 2017-08			$ (2)					$ (10)			$ 8
Common stock dividends, amount per share	$ 0.51
Net income (loss)	$ 1,337					1,337
Share-based compensation	72			72
Other comprehensive income	(721)								(721)
Common stock repurchases	(740)											(740)
Common stock dividends	(206)					(206)
Equity	$ 14,316			21,403		(4,682)			84			(2,489)
Common stock dividends, amount per share	$ 0.17
Net income (loss)	$ 381					381
Share-based compensation	14			14
Other comprehensive income	(106)								(106)
Common stock repurchases	(300)											(300)
Common stock dividends	(67)					(67)
Equity	14,450			21,417		(4,368)			190			(2,789)
Equity	$ 14,416	$ 13,399		21,438	$ 21,438	(4,057)	$ (5,074)		123	$ 123		(3,088)	$ (3,088)
Equity | Accounting Standards Update 2016-13			$ (1,017)					$ (1,017)
Common stock dividends, amount per share	$ 0.57
Net income (loss)	$ 398					398
Share-based compensation	79			79
Other comprehensive income	(572)								(572)
Common stock repurchases	(105)											(105)
Common stock dividends	(217)					(217)
Equity	$ 13,826			21,499		(5,296)			815			(3,192)
Common stock dividends, amount per share	$ 0.19
Net income (loss)	$ 476					476
Share-based compensation	18			18
Other comprehensive income	120								120
Common stock repurchases	(1)											(1)
Common stock dividends	(73)					(73)
Equity	$ 14,126			$ 21,517		$ (4,893)			$ 695			$ (3,193)