Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	2 Months Ended	10 Months Ended	12 Months Ended
	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at beginning of period	$ 20		$ 21
Tax positions of prior periods netted against deferred tax assets	0		950
(Decrease) increase in tax positions taken in the prior period	1		(1)
Increase in tax positions taken in the current period	0		3
Decrease due to settlement/payments	0		(1)
Decrease from the lapse of statute of limitations	0		(2)
Unrecognized tax benefits at end of period	21	$ 20	$ 970
Predecessor
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at beginning of period	$ 20	18
Tax positions of prior periods netted against deferred tax assets		0
(Decrease) increase in tax positions taken in the prior period		0
Increase in tax positions taken in the current period		2
Decrease due to settlement/payments		0
Decrease from the lapse of statute of limitations		0
Unrecognized tax benefits at end of period		$ 20