Shareholders' Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of the components of accumulated other comprehensive income (loss), net of tax
Balance at beginning of period	$ (75.9)	$ (44.2)	$ 28.2
Other comprehensive income (loss)	98.1	(35.7)	(86.4)
Realized loss on reclassification	4.8	4.0	14.0
Balance at end of period	27.0	(75.9)	(44.2)
Foreign Currency Translation
Summary of the components of accumulated other comprehensive income (loss), net of tax
Balance at beginning of period	(24.1)	3.2	66.0
Other comprehensive income (loss)	96.3	(27.3)	(62.8)
Balance at end of period	72.2	(24.1)	3.2
Pension Liability Adjustment
Summary of the components of accumulated other comprehensive income (loss), net of tax
Balance at beginning of period	(51.8)	(47.4)	(37.8)
Other comprehensive income (loss)	1.8	(8.4)	(23.6)
Realized loss on reclassification	4.8	4.0	14.0
Balance at end of period	$ (45.2)	$ (51.8)	$ (47.4)