Income Taxes - Income Tax Expense (Benefit) by Current and Deferred (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended		10 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Oct. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal
Current	$ 0
Deferred	231
State
Current	2
Deferred	6
Foreign
Current	4
Deferred	(9)
Total income tax expense (benefit)	$ 234	$ 16	$ (40)
Predecessor
Federal
Current				$ 0	$ 0	$ 0
Deferred				193	177	(2,941)
State
Current				7	4	3
Deferred				16	27	(246)
Foreign
Current				39	41	33
Deferred				13	(84)	1
Total income tax expense (benefit)				$ 268	$ 165	$ (3,150)