Equity Equity (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		43 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Jan. 01, 2018
Statement of Equity Table [Line Items]
Beginning Balance		114,620,499		114,620,499
Repurchase of common stock		(1,200,000)				(35,500,000)
Ending Balance	114,335,466			114,335,466		114,335,466
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 2,253	$ 2,315	$ 2,442	$ 2,315	$ 2,622
Cumulative Effect of New Accounting Principle in Period of Adoption							$ (22)
Net (loss) income	(69)		104	(98)	161
Other comprehensive income (loss)	(1)		0	0	(1)
Repurchase of common stock		$ (20)	(102)	(20)	(302)	$ (896)
Stock-based compensation	10		10	25	31
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures				0	0
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation				6	10
Dividends declared, APIC	(10)		(11)	(31)	(34)
Dividends declared	(10)		(11)	(33)	(36)
Ending Balance	$ 2,183		$ 2,443	$ 2,183	$ 2,443	$ 2,183
Common Stock
Statement of Equity Table [Line Items]
Beginning Balance	114,300,000	114,600,000	124.6	114,600,000	131.6
Repurchase of common stock			(4.7)	(1,200,000)	(12.5)
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures				1,300,000	1.2
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligations				(400,000)	(0.4)
Ending Balance	114,300,000		119.9	114,300,000	119.9	114,300,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1	$ 1	$ 1	$ 1	$ 1
Repurchase of common stock			0	0	0
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures				0	0
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation				0	0
Ending Balance	1		1	1	1	$ 1
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	4,837	4,869	5,073	4,869	5,285
Repurchase of common stock			(102)	(20)	(302)
Stock-based compensation	10		10	25	31
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation				6	10
Ending Balance	4,837		4,970	4,837	4,970	4,837
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(2,537)	(2,507)	(2,588)	(2,507)	(2,631)
Cumulative Effect of New Accounting Principle in Period of Adoption							(13)
Net (loss) income	(70)		103	(100)	159
Ending Balance	(2,607)		(2,485)	(2,607)	(2,485)	(2,607)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(51)	(52)	(47)	(52)	(37)
Cumulative Effect of New Accounting Principle in Period of Adoption							$ (9)
Other comprehensive income (loss)	(1)				(1)
Ending Balance	(52)		(47)	(52)	(47)	(52)
Non- controlling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	3	$ 4	3	4	4
Net (loss) income	1		1	2	2
Dividends declared, Noncontrolling Interest	0		0	(2)	2
Ending Balance	$ 4		$ 4	$ 4	$ 4	$ 4