Income Taxes (Details 6) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of unrecognized income tax benefits
Unrecognized tax benefits, beginning of year	$ 4	$ 0
Additions for income tax positions related to current year	0	1
Additions for income tax positions related to prior year	0	3
Reductions for income tax positions related to settlements	(4)	0
Unrecognized tax benefits, end of year	0	4	$ 0
Unrecognized tax benefits that, if recognized, would impact the effective tax rate	0	0
Recognized interest and penalties	2
Accrued interest and penalties		2
Maximum
Reconciliation of unrecognized income tax benefits
Recognized interest and penalties		$ (1)	$ 1
Accrued interest and penalties	$ 1