Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock	Noncontrolling Interest
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
Issuance of 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
Treasury stock	(7.5)					(7.5)
Distribution to noncontrolling interest	(3.3)						(3.3)
Ending balance (deficit) (in shares) at Dec. 31, 2016		22,356,586
Ending balance (deficit) at Dec. 31, 2016	268.4	$ 0.0	251.2	(1.4)	25.9	(7.5)	0.2
Increase (Decrease) in Stockholders' Equity
Cumulative effect adjustment upon adoption of new accounting standard on January 1, 2017	0.0		0.3		(0.3)
Stockholders' equity, adjusted balance	268.4	$ 0.0	251.5	(1.4)	25.6	(7.5)	0.2
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
Issuance of restricted stock units (in shares)		61,599
Issuance of restricted stock units	0.0
Issuance of performance stock units (in shares)		96,855
Issuance of performance 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)
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
Increase (Decrease) in Stockholders' Equity
Net income	56.4				53.2		3.2
Foreign currency translation adjustments	(0.6)			(0.6)
Issuance of stock grants (in shares)		20,757
Issuance of stock grants	0.7		0.7
Issuance of restricted stock units (in shares)		161,495
Issuance of restricted stock units	0.0
Issuance of performance stock units (in shares)		59,052
Issuance of performance stock units	0.0
Non-cash stock-based compensation related to restricted stock units and performance share units	2.4		2.4
Treasury stock	(7.5)
Distribution to noncontrolling interest	$ (3.3)						(3.3)
Ending balance (deficit) (in shares) at Dec. 31, 2018	22,783,976	22,783,976.000000
Ending balance (deficit) at Dec. 31, 2018	$ 368.6	$ 0.0	$ 257.7	$ (2.4)	$ 120.7	$ (7.5)	$ 0.1