Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock, Value, Outstanding	$ 53.1			$ 53.1
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0.8	$ (0.8)
Treasury Stock, Value	890.4			884.3
Stockholders' Equity Attributable to Noncontrolling Interest	31.9			32.2
Cumulative Effect of New Accounting Principle in Period of Adoption	7.7
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle	0.0
Shareholding pattern
Beginning Balance	1,474.9
Net income	80.5	38.1
Net (loss) income attributable to noncontrolling interest	0.3	(0.1)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	8.4	20.4
Net Income (Loss) Attributable to Parent	80.2	38.2
Pension and postretirement liability adjustment (net of the income tax benefit of $1.5 million)	0.0	0.1
Dividends - $0.26 per share	(21.1)
Stock-based compensation expense	10.3
Payments for Repurchase of Common Stock	(22.7)	(8.1)
Stock option exercise activity	(8.4)
Restricted shares surrendered (issued)	0.0
Payments Related to Tax Withholding for Share-based Compensation	4.4	8.2
Ending Balance	1,542.8
Additional Paid in Capital, Common Stock	901.5			903.8
Retained Earnings (Accumulated Deficit)	1,475.9		$ 1,416.1	1,408.4
Accumulated Other Comprehensive Income (Loss), Net of Tax	(29.2)	$ (60.8)		(38.3)	$ (77.9)
Stated Capital [Member]
Common Stock, Value, Outstanding	53.1
Other Paid-In Capital [Member]
Shareholding pattern
Stock-based compensation expense	10.3
Stock option exercise activity	(1.4)
Restricted shares surrendered (issued)	(11.2)
Additional Paid in Capital, Common Stock	901.5
Earnings Invested in the Business [Member]
Shareholding pattern
Dividends - $0.26 per share	(21.1)
Retained Earnings (Accumulated Deficit)	1,475.9
Accumulated Other Comprehensive (Loss) [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	0.8
Shareholding pattern
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	9.0
Accumulated Other Comprehensive Income (Loss), Net of Tax	(29.2)
Treasury Stock [Member]
Treasury Stock, Value	(890.4)
Shareholding pattern
Payments for Repurchase of Common Stock	(22.7)
Stock option exercise activity	(9.8)
Restricted shares surrendered (issued)	11.2
Payments Related to Tax Withholding for Share-based Compensation	4.4
Noncontrolling Interest [Member]
Stockholders' Equity Attributable to Noncontrolling Interest	31.9
Shareholding pattern
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(0.6)
Accounting Standards Update 2014-09 [Member]
Shareholding pattern
Net income	1.3
Net Income (Loss) Attributable to Parent	1.3
Retained Earnings (Accumulated Deficit)	9.0		$ 7.7
Accounting Standards Update 2014-09 [Member] | Earnings Invested in the Business [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	7.7
Accounting Standard Update 2018-02 [Member]
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle	(0.7)
Shareholding pattern
Accumulated Other Comprehensive Income (Loss), Net of Tax				$ (39.0)
Accounting Standard Update 2018-02 [Member] | Earnings Invested in the Business [Member]
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle	0.7
Accounting Standard Update 2018-02 [Member] | Accumulated Other Comprehensive (Loss) [Member]
Income Tax Effects Allocated Directly to Equity, Cumulative Effect of Change in Accounting Principle	$ (0.7)