Income Taxes Uncertain tax positions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Unrecognized Tax Benefits	$ 11	$ 38	$ 41	$ 40
Tax positions taken in current year	1	1	1
Tax positions taken in prior years	1	0	1
Tax positions taken in current year	0	0	0
Tax positions taken in prior years	0	0	0
Settlements during the year	0	(4)	(1)
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	29	0	$ 0
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 11
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		1
Unrecognized Tax Benefits, Interest on Income Taxes Expense		$ 2