Income Taxes - Net Operating Loss and Tax Credit Carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Tax Credit Carryforward [Line Items]
Excess interest	$ 9.1
Other deferred tax assets	2.7
Total tax carryforwards	181.9
Valuation Allowance [Abstract]
Excess interest	(2.9)
Other deferred tax assets	(3.1)
Total tax carryforwards	(141.2)
Domestic Tax Authority
Tax Credit Carryforward [Line Items]
Net operating loss not subject to expiration	0.2
Net operating loss subject to expiration	9.8
Tax credit carryforward	74.6
Alternative minimum tax credit	1.3
Valuation Allowance [Abstract]
Net operating loss not subject to expiration	0.0
Net operating loss subject to expiration	(2.1)
Tax credit carryforward	(74.6)
Alternative minimum tax credit		$ (0.1)
Domestic Tax Authority | Capital Loss Carryforward
Tax Credit Carryforward [Line Items]
Capital loss	7.6
Tax credit carryforward	0.8
Valuation Allowance [Abstract]
Capital loss	(7.6)
Tax credit carryforward	(0.8)
State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Net operating loss subject to expiration	3.0
Tax credit carryforward	0.3
Valuation Allowance [Abstract]
Net operating loss subject to expiration	(0.7)
Tax credit carryforward	0.0
Non U.S. Tax Authority
Tax Credit Carryforward [Line Items]
Net operating loss not subject to expiration	71.9
Valuation Allowance [Abstract]
Net operating loss not subject to expiration	(48.8)
Non U.S. Tax Authority | Capital Loss Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforward	0.6
Valuation Allowance [Abstract]
Tax credit carryforward	$ (0.5)