Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance (deficit)	$ 313.1	$ 268.4	$ 250.1
Change in other comprehensive income (loss)	(0.6)	0.2	(0.3)
Cumulative effect of change in accounting principle			0.0	$ 0.0
Ending balance (deficit)	368.6	313.1	268.4
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance (deficit)	(1.2)	(1.4)	(1.1)
Cumulative effect of change in accounting principle				(0.6)
Ending balance (deficit)	(2.4)	(1.2)	(1.4)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance (deficit)	(1.2)	(1.4)	(1.2)
Change in other comprehensive income (loss)	(0.6)	0.2	(0.2)
Cumulative effect of change in accounting principle				(0.6)
Ending balance (deficit)	(2.4)	(1.2)	(1.4)
Effective Portion of Unrealized Gain (Loss) on Derivative
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance (deficit)	0.0	0.0	0.1
Change in other comprehensive income (loss)	0.0	0.0	(0.1)
Cumulative effect of change in accounting principle				$ 0.0
Ending balance (deficit)	$ 0.0	$ 0.0	$ 0.0