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)	Stockholders' Equity	Non-controlling Interest
Balance at beginning of period at Dec. 31, 2014	$ 408	$ 14	$ 0	$ 3,014	$ (338)	$ (2,283)	$ 407	$ 1
Balance at beginning of period (in shares) at Dec. 31, 2014		144,768	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	991					991	991
Other comprehensive income (loss)	24				24		24
Share-based compensation	15			15			15
Stock issuances	7	$ 1	$ 8	(2)			7
Stock issuances (in shares)		899	283
Repurchase of common stock	(8)		$ (8)				(8)
Repurchase of common stock (in shares)			(283)
Changes in noncontrolling interest	(1)						0	(1)
Balance at end of period at Dec. 31, 2015	1,436	$ 15	$ 0	3,027	(314)	(1,292)	1,436	0
Balance at end of period (in shares) at Dec. 31, 2015		145,667	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	510					510	510
Other comprehensive income (loss)	(71)				(71)		(71)
Share-based compensation	18			18			18
Tax deficiencies in share-based compensation	(11)			(11)			(11)
Stock issuances	6	$ 0	$ 2	4			6
Stock issuances (in shares)		500	85
Repurchase of common stock	(2)		$ (2)				(2)
Repurchase of common stock (in shares)			(85)
Balance at end of period at Dec. 31, 2016	1,886	$ 15	$ 0	3,038	(385)	(782)	1,886	0
Balance at end of period (in shares) at Dec. 31, 2016		146,167	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact due to adoption of ASU 2016-09	25					25	25
Net income	88					88	88
Other comprehensive income (loss)	(4)				(4)		(4)
Share-based compensation	18			18			18
Stock issuances	14	$ 0	$ 19	(5)			14
Stock issuances (in shares)		346	577
Repurchase of common stock	(188)		$ (188)				(188)
Repurchase of common stock (in shares)			(6,148)
Other	6			6			6
Balance at end of period at Dec. 31, 2017	$ 1,845	$ 15	$ (169)	$ 3,057	$ (389)	$ (669)	$ 1,845	$ 0
Balance at end of period (in shares) at Dec. 31, 2017		146,513	(5,571)