Income Taxes - Net Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 185	$ 181
Additions based on tax positions related to the current year	3	4
Additions for tax positions of prior years	13	38
Reductions for tax positions of prior years	(37)	(38)
Statute of limitations	9	2
Settlements	(5)	(2)
Interest and penalties	(5)	0
Ending balance	145	185
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	139	154
Unrecognized tax benefits that would not impact the effective tax rate	$ 6	$ 31