Income Taxes - Reconciliation of Unrecognized Tax Benefits (Excluding Interest and Penalties) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 166	$ 73	$ 28
Additions for tax positions of the current year	34	0	23
Additions for tax positions of prior years	3	143	27
Reductions for tax positions of prior years	0	(42)	0
Settlements with tax authorities	0	0	0
Expiration of the statute of limitations	(2)	(6)	(5)
Foreign currency translation	(4)	(2)	0
Balance at end of year	$ 197	$ 166	$ 73