Earnings Per Share - Basic and Diluted EPS (Details) $ / shares in Units, shares in Thousands, $ in Millions		5 Months Ended	7 Months Ended	12 Months Ended
	Oct. 10, 2018	Dec. 31, 2018 USD ($) $ / shares shares	Jul. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Earnings Per Share [Abstract]
Reverse stock split ratio	0.083333
Net income attributable to Successor/Predecessor | $		$ 884	$ 154	$ 305	$ 274
Less: Undistributed earnings attributable to participating stockholders | $		8	0	3	2
Net income attributable to Successor/Predecessor common stockholders | $		$ 876	$ 154	$ 302	$ 272
Net income per common share attributable to Successor/Predecessor common stockholders:
Basic (in dollars per share) | $ / shares		$ 9.65	$ 1.57	$ 3.31	$ 2.99
Diluted (in dollars per share) | $ / shares		$ 9.54	$ 1.55	$ 3.20	$ 2.95
Weighted average shares of common stock outstanding (in thousands):
Basic (in shares)		90,813	98,046	91,312	91,035
Dilutive effect of stock awards (in shares)		178	1,091	2,343	270
Dilutive effect of participating securities (in shares)		839	0	839	839
Diluted (in shares)		91,830	99,137	94,494	92,144