CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Total
BALANCE at Dec. 31, 2018	$ 411	$ (87,747)	$ 316,479	$ 268,904	$ 498,047
BALANCE (in shares) at Dec. 31, 2018	41,123,365
BALANCE (in shares) at Dec. 31, 2018		(4,229,653)
Increase (Decrease) in Stockholders' Equity
Net income				19,866	19,866
Issuance of Stock:
Issuance of shares for options exercised		$ 861	(61)		800
Issuance of shares for options exercised (in shares)		41,103
Issuance of restricted stock & performance stock		$ 817	1,189		2,006
Issuance of restricted stock & performance stock (in shares)		38,539
Shares received in lieu of tax withholding payment on vested restricted stock		$ (781)			(781)
Shares received in lieu of tax withholding payment on vested restricted stock (in shares)		(15,013)
Stock-based compensation			2,084		2,084
Dividends				(3,506)	(3,506)
Share repurchase		$ (3,321)			(3,321)
Share repurchase (in shares)		(67,394)
BALANCE at Mar. 31, 2019	$ 411	$ (90,171)	319,691	285,264	515,195
BALANCE (in shares) at Mar. 31, 2019	41,123,365
BALANCE (in shares) at Mar. 31, 2019		(4,232,418)
BALANCE at Dec. 31, 2018	$ 411	$ (87,747)	316,479	268,904	498,047
BALANCE (in shares) at Dec. 31, 2018	41,123,365
BALANCE (in shares) at Dec. 31, 2018		(4,229,653)
Increase (Decrease) in Stockholders' Equity
Net income					44,039
BALANCE at Jun. 30, 2019	$ 411	$ (93,947)	319,879	305,745	532,088
BALANCE (in shares) at Jun. 30, 2019	41,123,365
BALANCE (in shares) at Jun. 30, 2019		(4,268,984)
BALANCE at Mar. 31, 2019	$ 411	$ (90,171)	319,691	285,264	515,195
BALANCE (in shares) at Mar. 31, 2019	41,123,365
BALANCE (in shares) at Mar. 31, 2019		(4,232,418)
Increase (Decrease) in Stockholders' Equity
Net income				24,173	24,173
Issuance of Stock:
Issuance of shares for options exercised		$ 31	(11)		20
Issuance of shares for options exercised (in shares)		1,408
Issuance of restricted stock & performance stock		$ 1,486	(1,486)
Issuance of restricted stock & performance stock (in shares)		69,067
Shares received in lieu of tax withholding payment on vested restricted stock		$ (717)			(717)
Shares received in lieu of tax withholding payment on vested restricted stock (in shares)		(13,573)
Stock-based compensation			1,685		1,685
Dividends				(3,692)	(3,692)
Share repurchase		$ (4,576)			(4,576)
Share repurchase (in shares)		(93,468)
BALANCE at Jun. 30, 2019	$ 411	$ (93,947)	319,879	305,745	532,088
BALANCE (in shares) at Jun. 30, 2019	41,123,365
BALANCE (in shares) at Jun. 30, 2019		(4,268,984)
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
Increase (Decrease) in Stockholders' Equity
Net income				17,716	$ 17,716
Issuance of Stock:
Issuance of restricted stock & performance stock		$ 1,054	801		1,855
Issuance of restricted stock & performance stock (in shares)		43,902
Shares received in lieu of tax withholding payment on vested restricted stock		$ (622)			(622)
Shares received in lieu of tax withholding payment on vested restricted stock (in shares)		(14,722)
Stock-based compensation			2,134		2,134
Dividends				(3,844)	(3,844)
Share repurchase		$ (8,985)			(8,985)
Share repurchase (in shares)		(237,359)
BALANCE at Mar. 31, 2020	$ 411	$ (112,513)	323,103	382,042	593,043
BALANCE (in shares) at Mar. 31, 2020	41,123,365
BALANCE (in shares) at Mar. 31, 2020		(4,673,627)
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
Increase (Decrease) in Stockholders' Equity
Net income					$ 57,211
BALANCE at Jun. 30, 2020	$ 411	$ (112,104)	322,419	417,707	$ 628,433
BALANCE (in shares) at Jun. 30, 2020	41,123,365				41,123,365
BALANCE (in shares) at Jun. 30, 2020		(4,620,071)			4,620,071
Increase (Decrease) in Stockholders' Equity
Cumulative-effect adjustment				(515)	$ (515)
BALANCE at Mar. 31, 2020	$ 411	$ (112,513)	323,103	382,042	593,043
BALANCE (in shares) at Mar. 31, 2020	41,123,365
BALANCE (in shares) at Mar. 31, 2020		(4,673,627)
Increase (Decrease) in Stockholders' Equity
Net income				39,495	39,495
Issuance of Stock:
Issuance of shares for options exercised		$ 836	(280)		556
Issuance of shares for options exercised (in shares)		34,562
Issuance of restricted stock & performance stock		$ 2,048	(2,048)
Issuance of restricted stock & performance stock (in shares)		84,987
Shares received in lieu of tax withholding payment on vested restricted stock		$ (454)			(454)
Shares received in lieu of tax withholding payment on vested restricted stock (in shares)		(13,002)
Stock-based compensation			1,644		1,644
Dividends				(3,830)	(3,830)
Share repurchase		$ (2,021)			(2,021)
Share repurchase (in shares)		(52,991)
BALANCE at Jun. 30, 2020	$ 411	$ (112,104)	$ 322,419	$ 417,707	$ 628,433
BALANCE (in shares) at Jun. 30, 2020	41,123,365				41,123,365
BALANCE (in shares) at Jun. 30, 2020		(4,620,071)			4,620,071