CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (DEFICIT) (unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]
Cumulative effect of adopting new hedging standard						$ 0.0
Beginning Balance at Dec. 31, 2016	$ 149.8	$ 3.1	$ 2,855.4	$ (2.4)	$ (2,980.5)	(88.7)	$ 362.9
Net income	193.0				161.6		31.4
Share-based compensation	5.5	0.1	5.4
Stock options exercised	0.5		0.5
Exchangeable notes exchange feature	21.3		21.3
Purchase of treasury stock	(3.0)			(3.0)
Change in accumulated other comprehensive income (loss)	(39.2)					(39.2)
Net distributions to noncontrolling interests	(41.9)						(41.9)
Ending Balance at Jun. 30, 2017	286.0	3.2	2,882.6	(5.4)	(2,818.9)	(127.9)	352.4
Cumulative effect of adopting new hedging standard						0.0
Net income	92.4
Ending Balance at Jun. 30, 2017	286.0	3.2	2,882.6	(5.4)	(2,818.9)	(127.9)	352.4
Cumulative effect of adopting new hedging standard	0.0				(0.8)	0.8
Beginning Balance at Dec. 31, 2017	300.6	3.2	2,884.8	(5.4)	(2,877.0)	(50.2)	345.2
Net income	117.1				85.3		31.8
Share-based compensation	6.3		6.3
Purchase of treasury stock	(1.0)			(1.0)
Change in accumulated other comprehensive income (loss)	(17.4)					(17.4)
Net distributions to noncontrolling interests	(34.8)						(34.8)
Ending Balance at Jun. 30, 2018	370.8	3.2	2,891.1	(6.4)	(2,792.5)	(66.8)	342.2
Cumulative effect of adopting new hedging standard						0.0
Net income	72.3
Ending Balance at Jun. 30, 2018	$ 370.8	$ 3.2	$ 2,891.1	$ (6.4)	$ (2,792.5)	$ (66.8)	$ 342.2