Shareholders' Equity - Accumulated Other Comprehensive Income (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($)
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	$ 733.5
Balance at end of period	825.2
Accumulated Other Comprehensive Income
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	27.0
Other comprehensive income (loss) before reclassifications	(16.2)
Amount reclassified from other comprehensive income (loss), net of tax of $0.3 million	1.9
Net current period other comprehensive income (loss)	(14.3)
Balance at end of period	12.7
Amount from reclassification, tax	0.3
Foreign Currency Translation
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	72.2
Other comprehensive income (loss) before reclassifications	(16.6)
Net current period other comprehensive income (loss)	(16.6)
Balance at end of period	55.6
Pension Liability Adjustment
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	(45.2)
Other comprehensive income (loss) before reclassifications	0.4
Amount reclassified from other comprehensive income (loss), net of tax of $0.3 million	1.9
Net current period other comprehensive income (loss)	2.3
Balance at end of period	$ (42.9)