Shareholders' Equity - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Components of Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation	$ (109.0)	$ (289.1)
Translation (loss) gain on net investment hedge, net of income taxes of $(19.8) and $11.2, respectively	(30.4)	24.8
Translation loss on long-term intercompany loans	(128.1)	(133.7)
Unrealized gain on investments, net of income taxes of $5.0 and $4.2, respectively	22.5	18.6
Accumulated other comprehensive loss	(290.6)	(426.1)
Translation gain (loss) on net investment hedge, tax	(19.8)	11.2
Unrealized gain (loss) on investments, tax	5.0	4.2
Defined benefit pension plans, net of income taxes of $(27.3) and $(27.8), respectively
Components of Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Defined benefit plans	(49.0)	(50.4)
Defined benefit plans, taxes	(27.3)	(27.8)
Retiree health care plan, net of income taxes of $1.9 and $2.1, respectively
Components of Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Defined benefit plans	3.4	3.7
Defined benefit plans, taxes	$ 1.9	$ 2.1