Income Taxes - Components of Pretax Income and Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
United States		$ 358	$ 299	$ 417
International		1,849	2,419	1,858
Income before income taxes		2,207	2,718	2,275
Current:
Federal		51	73	1,426
State and local		26	25	(17)
Foreign		221	245	151
Current income tax expense (benefit)		298	343	1,560
Deferred:
Federal		(269)	(488)	1,788
State and local		(45)	(10)	4
Foreign		431	345	(64)
Deferred income tax expense (benefit)		117	(153)	1,728
Income tax expense (benefit)	$ (445)	$ 415	$ 190	$ 3,288