Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2017	5,731,442
Balance at Dec. 31, 2017	$ 59	$ 28,412	$ 728,386	$ (80,058)	$ (352)	$ 676,447
Net income			40,653			40,653
Changes in pension, net of tax					1	1
Equity-based compensation		2,338				$ 2,338
Issuance of equity awards, net of forfeitures (in shares)	14,077
Repurchases of common stock (in shares)	(3,311)					(3,311)
Repurchases of common stock				(2,295)		$ (2,295)
Withholding tax for equity awards (in shares)	(9,767)					(9,767)
Withholding tax for equity awards				(7,199)		$ (7,199)
Dividends paid to stockholders			(10,035)			(10,035)
Balance (in shares) at Mar. 31, 2018	5,732,441
Balance at Mar. 31, 2018	$ 59	$ 30,750	$ 759,004	$ (89,552)	$ (351)	$ 699,910