Income Taxes - Unrecognized Tax Benefits Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits at beginning of period	$ 74	$ 79	$ 106
Additions based on tax positions related to the current year	0	0	0
Additions to tax positions of prior years	0	27	0
Settlements	0	(32)	0
Expiration of the applicable statute of limitations	0	0	(23)
Reductions to tax positions of prior years	0	0	(4)
Unrecognized tax benefits at end of period	$ 74	$ 74	$ 79