Condensed Consolidated Statement of Shareholders' Equity (unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Deferred Equity Compensation [Member]
Increase (Decrease) in Shareholders' Equity
Effect of adoption of ASU	$ (32)
Beginning balance (in shares) at Dec. 31, 2017		116,020,852
Beginning balance at Dec. 31, 2017	6,839	$ 1	$ 573	$ 5,892	$ 372	$ 1
Increase (Decrease) in Shareholders' Equity
Net income (loss)	197			197
Dividends ($0.18 per share in 2019 and $0.16 per share in 2018)	(19)			(19)
Common stock repurchases (in shares)		(2,787,936)
Common stock repurchases	(98)		(98)
Share-based compensation and other (in shares)		476,406
Share-based compensation and other	(9)		(9)
Other comprehensive income	(126)				(126)
Ending balance (in shares) at Mar. 31, 2018		113,709,322
Ending balance at Mar. 31, 2018	6,784	$ 1	466	6,102	214	1
Beginning balance (in shares) at Dec. 31, 2018		103,672,592
Beginning balance at Dec. 31, 2018	6,555	$ 1	86	6,374	93	1
Increase (Decrease) in Shareholders' Equity
Net income (loss)	54			54
Dividends ($0.18 per share in 2019 and $0.16 per share in 2018)	(19)			(19)
Common stock repurchases (in shares)		(1,908,605)
Common stock repurchases	(79)		(76)	(3)
Share-based compensation and other (in shares)		506,422
Share-based compensation and other	(10)		(10)
Other comprehensive income	168				168
Ending balance (in shares) at Mar. 31, 2019		102,270,409
Ending balance at Mar. 31, 2019	$ 6,669	$ 1	$ 0	$ 6,406	$ 261	$ 1