Income Taxes - Net Operating Losses (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
2018-2022	$ 6.2
2023-2027	4.9
2028 and thereafter	16.9
Unlimited	13.1
Tax benefit of net operating loss carryforwards before valuation allowances	41.1	$ 42.4
Federal
Operating Loss Carryforwards [Line Items]
2018-2022	0.0
2023-2027	0.0
2028 and thereafter	0.0
Unlimited	0.0
Tax benefit of net operating loss carryforwards before valuation allowances	0.0
State
Operating Loss Carryforwards [Line Items]
2018-2022	0.1
2023-2027	0.6
2028 and thereafter	15.8
Unlimited	0.0
Tax benefit of net operating loss carryforwards before valuation allowances	16.5
Foreign
Operating Loss Carryforwards [Line Items]
2018-2022	6.1
2023-2027	4.3
2028 and thereafter	1.1
Unlimited	13.1
Tax benefit of net operating loss carryforwards before valuation allowances	$ 24.6