Income Taxes - Schedule of Changes in Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 2,121	$ 2,357	$ 2,459
Increase to allowance	136	19	119
Release of allowance	(50)	(211)	(144)
Acquisitions and divestitures	0	(2)	0
Tax apportionment, tax rate and tax law changes	(23)	(13)	(14)
Foreign currency translation	123	(29)	(63)
Balance at end of year	$ 2,307	$ 2,121	$ 2,357