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 New Accounting Principle in Period of Adoption						$ 0.0
Balance at Dec. 31, 2016	$ 149.8	$ 3.1	$ 2,855.4	$ (2.4)	$ (2,980.5)	(88.7)	$ 362.9
Net income	100.6				84.4		16.2
Share-based compensation	4.2	0.1	4.1
Stock options exercised	0.3		0.3
Exchangeable notes exchange feature	1.6		1.6
Purchase of treasury stock	(2.9)			(2.9)
Change in accumulated other comprehensive income (loss)	(20.1)					(20.1)
Net distributions to noncontrolling interests	(15.1)						(15.1)
Balance at Mar. 31, 2017	218.4	3.2	2,861.4	(5.3)	(2,896.1)	(108.8)	364.0
Cumulative Effect of New Accounting Principle in Period of Adoption	0.0				(0.8)	0.8
Balance at Dec. 31, 2017	300.6	3.2	2,884.8	(5.4)	(2,877.0)	(50.2)	345.2
Net income	44.8				28.7		16.1
Share-based compensation	4.5		4.5
Purchase of treasury stock	(1.0)			(1.0)
Change in accumulated other comprehensive income (loss)	(6.7)					(6.7)
Net distributions to noncontrolling interests	(10.3)						(10.3)
Balance at Mar. 31, 2018	$ 331.9	$ 3.2	$ 2,889.3	$ (6.4)	$ (2,849.1)	$ (56.1)	$ 351.0