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	$ 0.8				$ (0.8)	$ 0.8
Beginning Balance at Dec. 31, 2017		$ 3.2	$ 2,884.8	$ (5.4)	(2,877.0)	(50.2)	$ 345.2
Share-based compensation			7.8
Stock options exercised			0.7
Purchase of treasury stock				(1.0)
Net income	152.5				152.5
Change in accumulated other comprehensive income (loss)	(18.3)					(18.3)
Net income attributable to noncontrolling interests	49.5						49.5
Net distributions to noncontrolling interests							(54.0)
Ending Balance at Sep. 30, 2018	437.8	3.2	2,893.3	(6.4)	(2,725.3)	(67.7)	340.7
Cumulative effect of adopting new hedging standard	0.0				0.0	0.0
Beginning Balance at Jun. 30, 2018		3.2	2,891.1	(6.4)	(2,792.5)	(66.8)	342.2
Share-based compensation			1.5
Stock options exercised			0.7
Purchase of treasury stock				0.0
Net income	67.2				67.2
Change in accumulated other comprehensive income (loss)	(0.9)					(0.9)
Net income attributable to noncontrolling interests	17.7						17.7
Net distributions to noncontrolling interests							(19.2)
Ending Balance at Sep. 30, 2018	437.8	3.2	2,893.3	(6.4)	(2,725.3)	(67.7)	340.7
Cumulative effect of adopting new hedging standard	0.0				0.0	0.0
Beginning Balance at Dec. 31, 2018	429.5	3.2	2,894.9	(6.4)	(2,691.8)	(100.0)	329.6
Share-based compensation			7.8
Stock options exercised			0.0
Purchase of treasury stock				(0.9)
Net income	65.1				65.1
Change in accumulated other comprehensive income (loss)	(37.3)					(37.3)
Net income attributable to noncontrolling interests	42.8						42.8
Net distributions to noncontrolling interests							(48.3)
Ending Balance at Sep. 30, 2019	458.7	3.2	2,902.7	(7.3)	(2,626.7)	(137.3)	324.1
Cumulative effect of adopting new hedging standard	0.0				0.0	0.0
Beginning Balance at Jun. 30, 2019		3.2	2,901.0	(7.2)	(2,629.5)	(131.9)	340.0
Share-based compensation			1.7
Stock options exercised			0.0
Purchase of treasury stock				(0.1)
Net income	2.8				2.8
Change in accumulated other comprehensive income (loss)	(5.4)					(5.4)
Net income attributable to noncontrolling interests	17.1						17.1
Net distributions to noncontrolling interests							(33.0)
Ending Balance at Sep. 30, 2019	$ 458.7	$ 3.2	$ 2,902.7	$ (7.3)	$ (2,626.7)	$ (137.3)	$ 324.1