Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Deficit)	Total Stockholders' Equity
Balance at beginning of period (in shares) at Dec. 31, 2015		145,667	0
Balance at beginning of period at Dec. 31, 2015		$ 15	$ 0	$ 3,027	$ (314)	$ (1,292)	$ 1,436
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 510					510	510
Other comprehensive loss	(71)				(71)		(71)
Share-based compensation				18			18
Tax deficiencies in share-based compensation				(11)			(11)
Stock issuances (in shares)		500	85
Stock issuances			$ 2	4			6
Repurchase of common stock (in shares)			(85)
Repurchase of common stock			$ (2)				(2)
Balance at end of period (in shares) at Dec. 31, 2016		146,167	0
Balance at end of period at Dec. 31, 2016		$ 15	$ 0	3,038	(385)	(782)	1,886
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	88					88	88
Other comprehensive loss	(4)				(4)		(4)
Share-based compensation				18			18
Stock issuances (in shares)		346	577
Stock issuances			$ 19	(5)			14
Repurchase of common stock (in shares)			(6,148)
Repurchase of common stock			$ (188)				(188)
Other				6			6
Balance at end of period (in shares) at Dec. 31, 2017		146,513	(5,571)
Balance at end of period at Dec. 31, 2017	1,845	$ 15	$ (169)	3,057	(389)	(669)	1,845
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	196					196	196
Other comprehensive loss	6				6		6
Share-based compensation				21			21
Stock issuances (in shares)			1,682
Stock issuances			$ 60	(48)			12
Repurchase of common stock (in shares)			(2,553)
Repurchase of common stock			$ (91)				(91)
Conditional special dividend						(72)	(72)
Balance at end of period (in shares) at Dec. 31, 2018		146,513	(6,442)
Balance at end of period at Dec. 31, 2018	$ 1,919	$ 15	$ (200)	$ 3,030	$ (383)	$ (543)	$ 1,919