Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ (274.7)	$ 436.4	$ (159.6)	$ 482.3
Net Income (Loss)	(131.9)	(65.6)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(1.1)	(9.2)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		0.0
Other Comprehensive Income Loss, Net Of Tax And Noncontrolling Interest Adjustment	1.6	(9.2)
Stock Issued During Period, Shares, Restricted Stock Award, Gross	0.0	0.0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	9.3	13.7
Dividends, Common Stock, Cash		(7.7)
Adoption of accounting standard		33.6
Treasury shares	(1.1)	(2.5)
Reclassification Of Temporary Equity To Liability	(0.6)	(4.4)
Distributions to noncontrolling interest holders		(0.5)
Reclassification From Noncontrolling Interests To Redeemable Noncontrolling Interests	10.6
Noncontrolling Interest, Decrease from Deconsolidation	(3.0)	(3.3)
Common Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	114.9	113.8	114.2	113.2
Stock Issued During Period, Shares, Restricted Stock Award, Gross	0.7	0.6
Additional Paid-in Capital [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	761.0	734.6	741.8	721.5
Stock Issued During Period, Shares, Restricted Stock Award, Gross	(0.7)	(0.6)
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	9.3	13.7
Reclassification From Noncontrolling Interests To Redeemable Noncontrolling Interests	10.6
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(301.0)	327.2	(168.3)	374.5
Net Income (Loss)	(132.7)	(73.2)
Dividends, Common Stock, Cash		(7.7)
Treasury Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(571.5)	(569.9)	(570.4)	(567.4)
Treasury shares	(1.1)	(2.5)
AOCI Attributable to Parent
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(304.8)	(205.5)	(303.7)	(196.3)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(1.1)	(9.2)
Parent [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(301.4)	400.2	(186.4)	445.5
Net Income (Loss)	(132.7)	(73.2)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(1.1)	(9.2)
Stock Issued During Period, Shares, Restricted Stock Award, Gross	0.0	0.0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	9.3	13.7
Dividends, Common Stock, Cash		(7.7)
Treasury shares	(1.1)	(2.5)
Reclassification Of Temporary Equity To Liability	0.0	0.0
Distributions to noncontrolling interest holders		0.0
Reclassification From Noncontrolling Interests To Redeemable Noncontrolling Interests	10.6
Noncontrolling Interest, Decrease from Deconsolidation	0.0	0.0
Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	26.7	36.2	$ 26.8	$ 36.8
Net Income (Loss)	0.8	7.6
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	2.7
Reclassification Of Temporary Equity To Liability	(0.6)	(4.4)
Distributions to noncontrolling interest holders		(0.5)
Reclassification From Noncontrolling Interests To Redeemable Noncontrolling Interests	0.0
Noncontrolling Interest, Decrease from Deconsolidation	(3.0)	(3.3)
Accounting Standards Update 2018-02 | AOCI Attributable to Parent
Adoption of accounting standard	$ 0.0	$ (29.0)