Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Increase (Decrease) in Stockholders' Equity
Beginning balance	$ 805.2	$ 698.6	$ 675.7
Ending balance	889.0	805.2	698.6
Foreign currency loss	0.4	3.9	0.5
Accumulated other comprehensive loss
Increase (Decrease) in Stockholders' Equity
Beginning balance	(8.1)	(35.2)	(24.9)
Other comprehensive income (loss) before reclassifications, net of a tax expense	(24.6)	25.0
Amounts reclassified from accumulated other comprehensive loss, net of taxes	2.8	2.1
Net current-period other comprehensive loss, net of taxes	(21.8)	27.1
Ending balance	(29.9)	(8.1)	(35.2)
Accumulated other comprehensive loss | Reclassification out of AOCI
Increase (Decrease) in Stockholders' Equity
Foreign currency loss		1.3
Foreign currency translation adjustments
Increase (Decrease) in Stockholders' Equity
Beginning balance	2.2	(24.7)
Other comprehensive income (loss) before reclassifications, net of a tax expense	(21.6)	25.6
Amounts reclassified from accumulated other comprehensive loss, net of taxes	1.9	1.3
Net current-period other comprehensive loss, net of taxes	(19.7)	26.9
Ending balance	(17.5)	2.2	(24.7)
Pension liability adjustments, net of taxes
Increase (Decrease) in Stockholders' Equity
Beginning balance	(10.3)	(10.5)
Other comprehensive income (loss) before reclassifications, net of a tax expense	(3.0)	(0.6)
Amounts reclassified from accumulated other comprehensive loss, net of taxes	0.9	0.8
Net current-period other comprehensive loss, net of taxes	(2.1)	0.2
Ending balance	$ (12.4)	$ (10.3)	$ (10.5)