Shareholders' Equity - Schedule of Other Comprehensive Income Included (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 536.2	$ 543.1	$ 549.7
Unrealized net gains (losses) arising during the period	(1.9)	9.5
Amounts reclassified from AOCL	1.5	(1.9)
Other comprehensive income (loss)	(0.4)	7.6	(6.4)
Ending balance	583.1	536.2	543.1
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(26.6)	(30.3)
Unrealized net gains (losses) arising during the period	2.1	4.7
Amounts reclassified from AOCL	0.3	(1.0)
Other comprehensive income (loss)	2.4	3.7
Ending balance	(24.2)	(26.6)	(30.3)
Retirement liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6.2)	(10.1)
Unrealized net gains (losses) arising during the period	(3.9)	5.2
Amounts reclassified from AOCL	1.0	(1.3)
Other comprehensive income (loss)	(2.9)	3.9
Ending balance	(9.1)	(6.2)	(10.1)
Interest rate cap
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(0.3)	(0.3)
Unrealized net gains (losses) arising during the period	(0.1)	(0.4)
Amounts reclassified from AOCL	0.2	0.4
Other comprehensive income (loss)	0.1	0.0
Ending balance	(0.2)	(0.3)	(0.3)
AOCL
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(33.1)	(40.7)	(33.5)
Other comprehensive income (loss)	(0.4)	7.6	(6.4)
Ending balance	$ (33.5)	$ (33.1)	$ (40.7)