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]	Parent [Member]	Noncontrolling Interest [Member]
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	$ 6,555	$ 0
Increase (Decrease) in Shareholders' Equity
Net Income (Loss)	54			54			54
Dividends (in dollars per share)	(19)			(19)			(19)
Share-based compensation and other (in shares)		506,422
Share-based compensation and other	(10)		(10)				(10)
Common stock repurchases (in shares)		(1,908,605)
Common stock repurchases	(79)		(76)	(3)			(79)
Other comprehensive loss	168				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	6,669	0
Beginning balance (in shares) at Dec. 31, 2019		93,274,987
Beginning balance at Dec. 31, 2019	6,645	$ 1		6,295	342	1	6,639	6
Increase (Decrease) in Shareholders' Equity
Net Income (Loss)	(56)			(55)			(55)	(1)
Dividends (in dollars per share)	(19)			(19)			(19)
Share-based compensation and other (in shares)		337,745
Share-based compensation and other	(5)			(5)			(5)
Common stock repurchases (in shares)		(3,629,410)
Common stock repurchases	(116)			(116)			(116)
Other comprehensive loss	(204)				(204)		(204)
Contributions and reallocation of ownership interests	20							20
Ending balance (in shares) at Mar. 31, 2020		89,983,322
Ending balance at Mar. 31, 2020	$ 6,265	$ 1		$ 6,100	$ 138	$ 1	$ 6,240	$ 25