Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 1,816.1	$ 1,792.9	$ 1,738.8
Increase (decrease)	44.6	22.0	(33.0)
Other comprehensive income (loss) before reclassifications, net of income taxes	44.6	22.0	(33.0)
Amounts reclassified from accumulated other comprehensive income (loss):
Increase (decrease)	0.5	0.4	0.5
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes:	0.5	0.4	0.5
Other comprehensive income (loss)	45.1	22.4	(32.5)
Ending balance	191.7	1,816.1	1,792.9
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	153.7	131.3	164.8
Increase (decrease)	44.6	22.4	(33.5)
Other comprehensive income (loss) before reclassifications, net of income taxes	44.6	22.4	(33.5)
Amounts reclassified from accumulated other comprehensive income (loss):
Increase (decrease)	0.0	0.0	0.0
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes:	0.0	0.0	0.0
Other comprehensive income (loss)	44.6	22.4	(33.5)
Ending balance	198.3	153.7	131.3
Pension & post- retirement plan benefit adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(5.0)	(5.0)	(6.0)
Increase (decrease)	0.0	(0.4)	0.5
Other comprehensive income (loss) before reclassifications, net of income taxes	0.0	(0.4)	0.5
Amounts reclassified from accumulated other comprehensive income (loss):
Increase (decrease)	0.5	0.4	0.5
Amounts reclassified from accumulated other comprehensive income (loss), net of income taxes:	0.5	0.4	0.5
Other comprehensive income (loss)	0.5	0.0	1.0
Ending balance	(4.5)	(5.0)	(5.0)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	148.7	126.3	158.8
Amounts reclassified from accumulated other comprehensive income (loss):
Other comprehensive income (loss)	45.1	22.4	(32.5)
Ending balance	$ 193.8	$ 148.7	$ 126.3