Income Taxes - Details of Scheduled Expiration Dates of Tax Effected Net Operating Loss (NOL) and Other Tax Carryforwards (Details) $ in Millions	Dec. 31, 2017 USD ($)
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Total	$ 41.3
U.S. federal
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Net Operating Loss	35.8
U.S. federal tax credit carryforwards	0.1
State taxing jurisdiction
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Net Operating Loss	2.3
U.S. federal and non-U.S.
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
U.S. federal and non-U.S. capital loss carryforwards	3.1
2018 Through 2027
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Total	4.4
2018 Through 2027 | U.S. federal
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Net Operating Loss	0.0
U.S. federal tax credit carryforwards	0.0
2018 Through 2027 | State taxing jurisdiction
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Net Operating Loss	1.4
2018 Through 2027 | U.S. federal and non-U.S.
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
U.S. federal and non-U.S. capital loss carryforwards	3.0
2028 Through 2037
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Total	36.8
2028 Through 2037 | U.S. federal
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Net Operating Loss	35.8
U.S. federal tax credit carryforwards	0.1
2028 Through 2037 | State taxing jurisdiction
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Net Operating Loss	0.9
2028 Through 2037 | U.S. federal and non-U.S.
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
U.S. federal and non-U.S. capital loss carryforwards	0.0
Indefinite
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Total	0.1
Indefinite | U.S. federal
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Net Operating Loss	0.0
U.S. federal tax credit carryforwards	0.0
Indefinite | State taxing jurisdiction
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
Net Operating Loss	0.0
Indefinite | U.S. federal and non-U.S.
Operating Loss Carryforwards And Other Tax Carryforwards [Line Items]
U.S. federal and non-U.S. capital loss carryforwards	$ 0.1