CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY (Unaudited) - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Total
Balance at Dec. 31, 2019	$ 191	$ 35,215	$ 318,572	$ (12,777)	$ 341,201
Balance (in shares) at Dec. 31, 2019	18,141,383
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, net		(428)		428
Exercise of stock options, net (in shares)	30,545
Stock-based compensation expense		873			873
Net income			2,020		2,020
Balance at Mar. 31, 2020	$ 191	35,660	320,592	(12,349)	344,094
Balance (in shares) at Mar. 31, 2020	18,171,928
Balance at Dec. 31, 2019	$ 191	35,215	318,572	(12,777)	341,201
Balance (in shares) at Dec. 31, 2019	18,141,383
Increase (Decrease) in Stockholders' Equity
Net income					(2,327)
Balance at Jun. 30, 2020	$ 191	36,089	316,245	(12,103)	340,422
Balance (in shares) at Jun. 30, 2020	18,189,562
Balance at Mar. 31, 2020	$ 191	35,660	320,592	(12,349)	344,094
Balance (in shares) at Mar. 31, 2020	18,171,928
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, net		(552)		246	(306)
Exercise of stock options, net (in shares)	17,634
Stock-based compensation expense		981			981
Net income			(4,347)		(4,347)
Balance at Jun. 30, 2020	$ 191	36,089	316,245	(12,103)	340,422
Balance (in shares) at Jun. 30, 2020	18,189,562
Balance at Dec. 31, 2020	$ 191	34,498	342,250	(8,872)	$ 368,067
Balance (in shares) at Dec. 31, 2020	18,426,130				18,426,130
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, net		1,143		1,266	$ 2,409
Exercise of stock options, net (in shares)	91,831
Stock-based compensation expense		1,280			1,280
Net income			8,154		8,154
Balance at Mar. 31, 2021	$ 191	36,921	350,404	(7,606)	379,910
Balance (in shares) at Mar. 31, 2021	18,517,961
Balance at Dec. 31, 2020	$ 191	34,498	342,250	(8,872)	$ 368,067
Balance (in shares) at Dec. 31, 2020	18,426,130				18,426,130
Increase (Decrease) in Stockholders' Equity
Net income					$ 26,303
Balance at Jun. 30, 2021	$ 191	38,843	368,553	(6,500)	$ 401,087
Balance (in shares) at Jun. 30, 2021	18,599,516				18,599,516
Balance at Mar. 31, 2021	$ 191	36,921	350,404	(7,606)	$ 379,910
Balance (in shares) at Mar. 31, 2021	18,517,961
Increase (Decrease) in Stockholders' Equity
Exercise of stock options, net		675		1,106	1,781
Exercise of stock options, net (in shares)	81,555
Stock-based compensation expense		1,247			1,247
Net income			18,149		18,149
Balance at Jun. 30, 2021	$ 191	$ 38,843	$ 368,553	$ (6,500)	$ 401,087
Balance (in shares) at Jun. 30, 2021	18,599,516				18,599,516