Income Taxes - Unrecognized Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 1.1
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Uncertain tax position balance at beginning of year	2.4	$ 0.9	$ 1.8
Increases related to current year tax positions	0.3	2.0	0.0
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	0.4	0.0	0.0
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(2.0)	0.0	0.0
Decreases related to expiration of statute of limitations	(0.1)	(0.5)	(0.9)
Uncertain tax position balance at end of year	1.0	$ 2.4	$ 0.9
Decrease in unrecognized tax benefits that may be recognized in next fiscal year	$ 0.2