Consolidated Statements of Changes in Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Income	Total Stockholders’ Equity	Non-controlling Interests	Series A Preferred Stock Preferred Stock	Series A Preferred Stock Common Stock	Series A Preferred Stock Additional Paid-In Capital
Balance at beginning of period (in shares) at Dec. 31, 2015		109,523						73
Balance at beginning of period at Dec. 31, 2015	$ 3,061	$ 0	$ 3,212	$ (465)	$ (72)	$ 2,717	$ 344	$ 42
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	85			69		69	16
Other comprehensive (loss) income	(141)				(122)	(122)	(19)
Repurchase of noncontrolling interest	3		3			3
Exercise and vesting of stock compensation awards (in shares)		1,298
Exercise and vesting of stock compensation awards	10		10			10
Tax withholdings related to vesting of stock compensation awards (in shares)		0
Tax withholdings related to vesting of stock compensation awards	(11)		(11)			(11)
Conversion of Series A preferred stock to common stock (in shares)								(1)	93
Issuance of common stock upon conversion of convertible senior notes, net of tax (in shares)		173
Issuance of common stock upon conversion of convertible senior notes, net of tax	3		3			3
Dividend paid	(6)			(3)		(3)	(3)
Adoption of stock compensation standard	7		1	6		7
Stock compensation expense	27		27			27
Balance at end of period (in shares) at Dec. 31, 2016		111,087						72
Balance at end of period at Dec. 31, 2016	3,038	$ 0	3,245	(393)	(194)	2,700	338	$ 42
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	360			340		340	20
Other comprehensive (loss) income	275				223	223	52
Exercise and vesting of stock compensation awards (in shares)		728
Exercise and vesting of stock compensation awards	1		1			1
Tax withholdings related to vesting of stock compensation awards (in shares)		0
Tax withholdings related to vesting of stock compensation awards	(17)		(17)			(17)
Issuance of common stock from offering (in shares)		5,000
Issuance of common stock from offering	288		288			288
Conversion of Series A preferred stock to common stock (in shares)									103
Conversion of Series A preferred stock to common stock								$ (1)		$ 1
Issuance of common stock upon conversion of convertible senior notes, net of tax (in shares)		3,002
Issuance of common stock upon conversion of convertible senior notes, net of tax	49		49			49
Dividend paid	(7)			(3)		(3)	(4)
Impact of tax reform act				13	(13)
Stock compensation expense	23		23			23
Balance at end of period (in shares) at Dec. 31, 2017		119,920						72
Balance at end of period at Dec. 31, 2017	4,010	$ 0	3,590	(43)	16	3,604	406	$ 41
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	444			422		422	22
Other comprehensive (loss) income	(197)				(170)	(170)	(27)
Exercise and vesting of stock compensation awards (in shares)		995
Exercise and vesting of stock compensation awards	1		1			1
Tax withholdings related to vesting of stock compensation awards	(53)		(53)			(53)
Issuance of common stock from offering (in shares)		6,000
Issuance of common stock from offering	349		349			349
Retirement of common stock (in shares)		(11,314)
Retirement of common stock	(608)		(608)			(608)
Dividend paid	(9)			(3)		(3)	(6)
Stock compensation expense	30		30			30
Other (in shares)		82
Other	3		2	1		3
Balance at end of period (in shares) at Dec. 31, 2018		115,683						72
Balance at end of period at Dec. 31, 2018	$ 3,970	$ 0	$ 3,311	$ 377	$ (154)	$ 3,575	$ 395	$ 41