CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Total
BALANCE at Dec. 31, 2016	$ 411	$ (57,387)	$ 309,625	$ 123,984	$ 376,633
BALANCE (in shares) at Dec. 31, 2016	41,123,365
BALANCE (in shares) at Dec. 31, 2016		(3,914,251)
Increase (Decrease) in Stockholders' Equity
Net income				55,272	55,272
Issuance of Stock:
Issuance of shares for options exercised		$ 2,257	(205)		2,052
Issuance of shares for options exercised (in shares)		145,746
Issuance of restricted stock & performance stock		$ 2,037	(421)		1,616
Issuance of restricted stock & performance stock (in shares)		134,646
Shares received in lieu of tax withholding payment on vested restricted stock		$ (1,419)			(1,419)
Shares received in lieu of tax withholding payment on vested restricted stock (in shares)		(39,335)
Stock-based compensation			3,785		3,785
Dividends				(10,987)	(10,987)
Share repurchase		$ (9,007)			(9,007)
Share repurchase (in shares)		(263,097)
BALANCE at Dec. 31, 2017	$ 411	$ (63,519)	312,784	168,269	417,945
BALANCE (in shares) at Dec. 31, 2017	41,123,365
BALANCE (in shares) at Dec. 31, 2017		(3,936,291)
Increase (Decrease) in Stockholders' Equity
Net income				112,903	112,903
Issuance of Stock:
Issuance of shares for options exercised		$ 3,618	(513)		3,105
Issuance of shares for options exercised (in shares)		206,875
Issuance of restricted stock & performance stock		$ 2,227	(4)		2,223
Issuance of restricted stock & performance stock (in shares)		129,569
Shares received in lieu of tax withholding payment on vested restricted stock		$ (1,540)			(1,540)
Shares received in lieu of tax withholding payment on vested restricted stock (in shares)		(36,967)
Stock-based compensation			4,212		4,212
Dividends				(12,268)	(12,268)
Share repurchase		$ (28,533)			(28,533)
Share repurchase (in shares)		(592,839)
BALANCE at Dec. 31, 2018	$ 411	$ (87,747)	316,479	268,904	$ 498,047
BALANCE (in shares) at Dec. 31, 2018	41,123,365				41,123,365
BALANCE (in shares) at Dec. 31, 2018		(4,229,653)			4,229,653
Increase (Decrease) in Stockholders' Equity
Net income				114,324	$ 114,324
Issuance of Stock:
Issuance of shares for options exercised		$ 2,532	(182)		2,350
Issuance of shares for options exercised (in shares)		114,125
Issuance of restricted stock & performance stock		$ 2,303	(297)		2,006
Issuance of restricted stock & performance stock (in shares)		107,606
Shares received in lieu of tax withholding payment on vested restricted stock		$ (1,498)			(1,498)
Shares received in lieu of tax withholding payment on vested restricted stock (in shares)		(28,586)
Stock-based compensation			4,168		4,168
Dividends				(14,543)	(14,543)
Share repurchase		$ (19,550)			(19,550)
Share repurchase (in shares)		(428,940)
BALANCE at Dec. 31, 2019	$ 411	$ (103,960)	$ 320,168	$ 368,685	$ 585,304
BALANCE (in shares) at Dec. 31, 2019	41,123,365				41,123,365
BALANCE (in shares) at Dec. 31, 2019		(4,465,448)			4,465,448