Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Tax Reform Act Tax Expense Charge	$ 92.0
Gross amount of the net operating loss carryforwards	372.2	$ 372.2
Net operating loss carryforwards	41.1	41.1	$ 42.4
Potential benefits	9.7	9.7
Interest and penalties included in income tax expense		(0.3)	0.1	$ (0.1)
Accrued penalties and interest	0.8	0.8	$ 0.9
Currently remaining unrecognized tax positions that may be recognized by the end of following year		$ 1.4
Tax Cuts and Jobs Act of 2017
Operating Loss Carryforwards [Line Items]
Tax Reform Act Tax Expense Charge	$ 92.0