Shareholders' Equity - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Components of Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation		$ (40.0)		$ (87.7)
Translation loss on net investment hedge, net of income taxes of $(27.9) and $(23.1), respectively		(56.3)		(39.9)
Translation loss on long-term intercompany loans		(121.2)		(128.8)
Unrealized gain on investments, net of income taxes of $3.4 for 2017		0.0		15.3
Defined Benefit Plan Disclosure [Line Items]
Accumulated Other Comprehensive Income Translation Gain Loss on Net Investment Hedge, Tax		(27.9)		(23.1)
Unrealized Gain (Loss) on Investments, Tax				3.4
Accumulated other comprehensive loss		(264.1)		(288.2)
Reclassification of cumulative unrealized gain as of December 31, 2017 from accumulated other comprehensive loss to retained earnings	$ 15.3	15.3	$ 0.0
Defined benefit pension plans, net of income taxes of $(27.7) and $(27.8), respectively
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plans		(49.9)		(50.5)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Tax		(27.6)		(27.8)
Retiree health care plan, net of income taxes of $2.0 and $2.1, respectively
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plans		3.3		3.4
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Tax		$ 2.0		$ 2.0