Shareholders' Equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	$ 905.1	$ 733.5
Net current period other comprehensive income (loss)	(13.7)	24.3
Balance at end of period	921.6	790.3
Accumulated Other Comprehensive Income (Loss)
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	17.0	27.0
Other comprehensive income (loss) before reclassifications	(14.1)
Amounts reclassified from other comprehensive income (loss), net of tax of $0.0 million	0.4
Net current period other comprehensive income (loss)	(13.7)	24.2
Balance at end of period	3.3	$ 51.2
Amount from reclassification, tax	0.0
Foreign Currency Translation
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	46.9
Other comprehensive income (loss) before reclassifications	(14.5)
Net current period other comprehensive income (loss)	(14.5)
Balance at end of period	32.4
Pension Liability Adjustment
Summary of the components of accumulated other comprehensive income, net of tax
Balance at beginning of period	(29.9)
Other comprehensive income (loss) before reclassifications	0.4
Amounts reclassified from other comprehensive income (loss), net of tax of $0.0 million	0.4
Net current period other comprehensive income (loss)	0.8
Balance at end of period	$ (29.1)