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, 2016		22,356,586
Beginning 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
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
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
Distribution to noncontrolling interest	$ (3.3)						(3.3)
Ending balance (deficit) (in shares) at Dec. 31, 2018	22,783,976	22,783,976
Ending balance (deficit) at Dec. 31, 2018	$ 368.6	$ 0.0	257.7	(2.4)	120.7	(7.5)	0.1
Increase (Decrease) in Stockholders' Equity
Cumulative effect adjustment upon adoption of new accounting standard	(0.6)
Net income	51.7				48.8		2.9
Foreign currency translation adjustments	0.1			0.1
Effective portion of cash flow hedge	(0.4)			(0.4)
Issuance of stock grants (in shares)		14,076
Issuance of stock grants	0.8		0.8
Issuance of restricted stock units (in shares)		90,214
Issuance of restricted stock units	0.0
Issuance of performance stock units (in shares)		62,094
Issuance of performance stock units	0.0
Non-cash stock-based compensation related to restricted stock units and performance share units	4.1		4.1
Treasury stock	(47.8)					$ (47.9)
Distribution to noncontrolling interest	$ (3.2)						(3.2)
Ending balance (deficit) (in shares) at Dec. 31, 2019	22,950,360	22,950,360
Ending balance (deficit) at Dec. 31, 2019	$ 373.9	$ 0.0	$ 262.6	$ (2.7)	$ 169.5		$ (0.2)