Consolidated Statements of Changes in Stockholder's Equity Statement - USD ($)	Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]
Beginning balance (in shares) at Jan. 01, 2017		35,258,579
Beginning balance at Jan. 01, 2017	$ 154,656,000	$ 353,000	$ 0	$ 141,133,000	$ 14,514,000	$ (1,203,000)	$ (141,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2016-09	3,734,000				3,734,000
Stock-based compensation	3,518,000	$ 0	0	3,518,000	0	0	0
Vesting of non-vested shares and excess tax benefits (in shares)		177,673
Vesting of non-vested shares and excess tax benefits	0	$ 1,000	0	(1,000)	0	0	0
Net income	7,159,000	0	0	0	7,159,000	0	0
Change in postretirement benefit obligations, net of tax benefit of $4	$ (7,000)	$ 0	0	0	0	(7,000)	0
Ending balance (in shares) at Dec. 31, 2017	35,436,252	35,436,252
Ending balance at Dec. 31, 2017	$ 169,060,000	$ 354,000	0	144,650,000	25,407,000	(1,210,000)	(141,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	4,501,000	$ 0	0	4,501,000	0	0	0
Vesting of non-vested shares and excess tax benefits (in shares)		306,175
Vesting of non-vested shares and excess tax benefits	0	$ 3,000	0	(3,000)	0	0	0
Net income	$ 8,297,000	$ 0	0	0	8,297,000	0	0
Ending balance (in shares) at Sep. 30, 2018	35,742,427	35,742,427
Ending balance at Sep. 30, 2018	$ 181,858,000	$ 357,000	$ 0	$ 149,148,000	$ 33,704,000	$ (1,210,000)	$ (141,000)