Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2019	12,885,273
Balance at Dec. 31, 2019	$ 129,000	$ 708,000	$ 32,390,000	$ 33,227,000
Net income			5,342,000	5,342,000
Common stock repurchased and retired (in shares)	(35,100)
Common stock repurchased and retired		(125,000)		(125,000)
Stock-based compensation expense		91,000		91,000
Options exercised (in shares)	712,839
Options exercised	$ 7,000	1,834,000		1,841,000
Balance as of March 31, 2021 (in shares) at Mar. 31, 2020	13,563,012
Balance at Mar. 31, 2020	$ 136,000	2,508,000	37,732,000	40,376,000
Balance (in shares) at Dec. 31, 2019	12,885,273
Balance at Dec. 31, 2019	$ 129,000	708,000	32,390,000	33,227,000
Net income				19,668,000
Balance as of March 31, 2021 (in shares) at Sep. 30, 2020	13,577,847
Balance at Sep. 30, 2020	$ 136,000	2,539,000	52,058,000	54,733,000
Balance (in shares) at Mar. 31, 2020	13,563,012
Balance at Mar. 31, 2020	$ 136,000	2,508,000	37,732,000	40,376,000
Net income			6,220,000	6,220,000
Stock-based compensation expense		92,000		92,000
Options exercised (in shares)	24,835
Options exercised		94,000		94,000
Balance as of March 31, 2021 (in shares) at Jun. 30, 2020	13,587,847
Balance at Jun. 30, 2020	$ 136,000	2,694,000	43,951,000	46,781,000
Net income			8,107,000	8,107,000
Common stock repurchased and retired (in shares)	(20,000)
Common stock repurchased and retired		(281,000)		(281,000)
Stock-based compensation expense		91,000		91,000
Options exercised (in shares)	10,000
Options exercised		35,000		35,000
Balance as of March 31, 2021 (in shares) at Sep. 30, 2020	13,577,847
Balance at Sep. 30, 2020	$ 136,000	2,539,000	52,058,000	$ 54,733,000
Balance (in shares) at Dec. 31, 2020	13,419,847			13,419,847	[1]
Balance at Dec. 31, 2020	$ 135,000	409,000	59,476,000	$ 60,020,000	[1]
Net income			3,719,000	3,719,000
Common stock repurchased and retired (in shares)	(186,000)
Common stock repurchased and retired	$ (2,000)	(817,000)	(1,547,000)	(2,366,000)
Stock-based compensation expense		101,000		101,000
Options exercised (in shares)	89,494
Options exercised	$ 1,000	307,000		308,000
Balance as of March 31, 2021 (in shares) at Mar. 31, 2021	13,323,341
Balance at Mar. 31, 2021	$ 134,000		61,648,000	$ 61,782,000
Balance (in shares) at Dec. 31, 2020	13,419,847			13,419,847	[1]
Balance at Dec. 31, 2020	$ 135,000	409,000	59,476,000	$ 60,020,000	[1]
Net income				$ 6,156,000
Options exercised (in shares)				124,494
Balance as of March 31, 2021 (in shares) at Sep. 30, 2021	13,162,341			13,162,341
Balance at Sep. 30, 2021	$ 132,000		62,596,000	$ 62,728,000
Balance (in shares) at Mar. 31, 2021	13,323,341
Balance at Mar. 31, 2021	$ 134,000		61,648,000	61,782,000
Net income			1,671,000	1,671,000
Common stock repurchased and retired (in shares)	(150,000)
Common stock repurchased and retired	$ (2,000)	(151,000)	(1,189,000)	(1,342,000)
Stock-based compensation expense		68,000		68,000
Options exercised (in shares)	35,000
Options exercised		83,000		83,000
Balance as of March 31, 2021 (in shares) at Jun. 30, 2021	13,208,341
Balance at Jun. 30, 2021	$ 132,000		62,130,000	62,262,000
Net income			766,000	766,000
Common stock repurchased and retired (in shares)	(46,000)
Common stock repurchased and retired		(69,000)	(300,000)	(369,000)
Stock-based compensation expense		$ 69,000		$ 69,000
Balance as of March 31, 2021 (in shares) at Sep. 30, 2021	13,162,341			13,162,341
Balance at Sep. 30, 2021	$ 132,000		$ 62,596,000	$ 62,728,000

[1] The condensed consolidated balance sheet as of December 31, 2020 has been prepared using information from the audited consolidated balance sheet as of that date.