Condensed Consolidated Statements of Stockholder's Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2019	$ 34,893	$ 50	$ 41,576	$ (6,153)	$ (580)
Balance (in shares) at Dec. 31, 2019		4,933,063
Net income	183			183
Exercise of stock options	58		58
Exercise of stock options (in shares)		14,000
At-the-market stock sales, net of costs	3,254	$ 3	3,251
At-the-market stock sales, net of costs (in shares)		263,725
Stock-based compensation	10		10
Balance at Mar. 31, 2020	38,398	$ 53	44,895	(5,970)	(580)
Balance (in shares) at Mar. 31, 2020		5,210,788
Balance at Dec. 31, 2019	34,893	$ 50	41,576	(6,153)	(580)
Balance (in shares) at Dec. 31, 2019		4,933,063
Net income	1,067
Balance at Sep. 30, 2020	39,386	$ 53	44,999	(5,086)	(580)
Balance (in shares) at Sep. 30, 2020		5,213,320
Balance at Mar. 31, 2020	38,398	$ 53	44,895	(5,970)	(580)
Balance (in shares) at Mar. 31, 2020		5,210,788
Net income	255			255
Exercise of stock options	5		5
Exercise of stock options (in shares)		1,266
Stock-based compensation	37		37
Balance at Jun. 30, 2020	38,695	$ 53	44,937	(5,715)	(580)
Balance (in shares) at Jun. 30, 2020		5,212,054
Net income	629			629
Exercise of stock options	5		5
Exercise of stock options (in shares)		1,266
Stock-based compensation	57		57
Balance at Sep. 30, 2020	39,386	$ 53	44,999	(5,086)	(580)
Balance (in shares) at Sep. 30, 2020		5,213,320
Balance at Dec. 31, 2020	$ 39,765	$ 53	45,477	(5,185)	(580)
Balance (in shares) at Dec. 31, 2020	5,272,204	5,272,204
Net income	$ 27			27
Stock-based compensation	78		78
Balance at Mar. 31, 2021	39,870	$ 53	45,555	(5,158)	(580)
Balance (in shares) at Mar. 31, 2021		5,272,204
Balance at Dec. 31, 2020	$ 39,765	$ 53	45,477	(5,185)	(580)
Balance (in shares) at Dec. 31, 2020	5,272,204	5,272,204
Net income	$ 31,789
Balance at Sep. 30, 2021	$ 71,701	$ 53	45,624	26,604	(580)
Balance (in shares) at Sep. 30, 2021	5,280,204	5,280,204
Balance at Mar. 31, 2021	$ 39,870	$ 53	45,555	(5,158)	(580)
Balance (in shares) at Mar. 31, 2021		5,272,204
Net income	(18)			(18)
Stock-based compensation	19		19
Balance at Jun. 30, 2021	39,871	$ 53	45,574	(5,176)	(580)
Balance (in shares) at Jun. 30, 2021		5,272,204
Net income	31,780			31,780
Exercise of stock options	31		31
Exercise of stock options (in shares)		8,000
Stock-based compensation	19		19
Balance at Sep. 30, 2021	$ 71,701	$ 53	$ 45,624	$ 26,604	$ (580)
Balance (in shares) at Sep. 30, 2021	5,280,204	5,280,204