Income Taxes - Reconciliation of Unrecognized Tax Benefits (Excluding Interest and Penalties) (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	$ 176	$ 148	$ 50
Additions for tax positions of the current year	0	34	0
Additions for tax positions of prior years	0	0	143
Reductions for tax positions of prior years	(182)	(1)	(38)
Settlements with tax authorities	(1)	0	0
Expiration of the statute of limitations	0	(2)	(6)
Foreign currency translation	9	(3)	(1)
Balance at end of year	$ 2	$ 176	$ 148