Income Taxes - Income Tax Expense (Benefit) on Continuing Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ (3)	$ (21)	$ 0
Foreign	7	2	5
State	2	2	1
Total current	6	(17)	6
Deferred:
Federal	23	243	41
Foreign	0	0	2
State	5	12	14
Total deferred	28	255	57
Provision for income tax expense (benefit)	$ 34	$ 238	$ 63