Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)	Treasury Stock	Noncontrolling Interest
Beginning balance (deficit) (in shares) at Dec. 31, 2014		22,127,725
Beginning balance (deficit) at Dec. 31, 2014	$ 229.8	$ 0.0	$ 243.9	$ (0.2)	$ (14.6)	$ 0.0	$ 0.7
Increase (Decrease) in Stockholders' Equity
Net income	20.3				17.4		2.9
Foreign currency translation adjustments	(0.7)			(0.7)
Effective portion of cash flow hedge	(0.2)			(0.2)
Issuance of stock grants (in shares)		29,305
Issuance of stock grants	0.7		0.7
Vested restricted stock units (in shares)		164,447
Issuance of restricted stock units	0.0
Proceeds from exercise of stock options (in shares)		7,101
Proceeds from exercise of stock options	0.0
Non-cash stock-based compensation related to restricted stock units and performance share units	3.0		3.0
Tax benefit from exercise of stock options	0.3		0.3
Distribution to noncontrolling interest	(3.1)						(3.1)
Ending balance (deficit) (in shares) at Dec. 31, 2015		22,328,578
Ending balance (deficit) at Dec. 31, 2015	250.1	$ 0.0	247.9	(1.1)	2.8	0.0	0.5
Increase (Decrease) in Stockholders' Equity
Net income	0.6
Beginning balance (deficit) (in shares) at Dec. 31, 2015		22,328,578
Beginning balance (deficit) at Dec. 31, 2015	250.1	$ 0.0	247.9	(1.1)	2.8	0.0	0.5
Increase (Decrease) in Stockholders' Equity
Net income	26.0				23.1		2.9
Foreign currency translation adjustments	(0.2)			(0.2)
Effective portion of cash flow hedge	(0.1)			(0.1)
Issuance of stock grants (in shares)		26,593
Issuance of stock grants	0.6		0.6
Vested restricted stock units (in shares)		1,415
Issuance of restricted stock units	0.0
Non-cash stock-based compensation related to restricted stock units and performance share units	2.7		2.7
Distribution to noncontrolling interest	(3.3)						(3.3)
Treasury stock	$ (7.5)					0.0
Ending balance (deficit) (in shares) at Dec. 31, 2016	22,356,856	22,356,586
Ending balance (deficit) at Dec. 31, 2016	$ 268.4	$ 0.0	251.2	(1.4)	25.9	(7.5)	0.2
Ending balance (deficit) (Adjustments for New Accounting Pronouncement) at Dec. 31, 2016			251.5		25.6
Increase (Decrease) in Stockholders' Equity
Cumulative effect adjustment upon adoption of new accounting standard on January 1, 2017 | Accounting Standards Update 2017-01	0.0		0.3		(0.3)
Net income	44.5				41.2		3.3
Foreign currency translation adjustments	0.2			0.2
Issuance of stock grants (in shares)		27,632
Issuance of stock grants	0.9		0.9
Vested restricted stock units (in shares)		61,599
Issuance of restricted stock units	0.0
Non-cash stock-based compensation related to restricted stock units and performance share units	2.2		2.2
Distribution to noncontrolling interest	(3.2)						(3.2)
Vested performance stock units (in shares)		96,855
Issuance of performance stock units	$ 0.0
Ending balance (deficit) (in shares) at Dec. 31, 2017	22,542,672	22,542,672
Ending balance (deficit) at Dec. 31, 2017	$ 313.1	$ 0.0	$ 254.6	$ (1.2)	$ 67.0	$ (7.5)	$ 0.2