Condensed Consolidated Statements of Stockholders' Deficit - USD ($) $ in Thousands	Common Stock	Capital deficiency	Accumulated earnings (loss)	Total
Beginning balance at Dec. 31, 2019	$ 11	$ (111,988)	$ (42,319)	$ (154,296)
Beginning balance (in shares) at Dec. 31, 2019	11,224,191
Shares issued under stock-based compensation plans (in shares)	6,291
Stock-based compensation		78		78
Components of comprehensive income:
Net income			8,844	8,844
Ending balance at Sep. 30, 2020	$ 11	(111,910)	(33,475)	(145,374)
Ending balance (in shares) at Sep. 30, 2020	11,230,482
Beginning balance at Jun. 30, 2020	$ 11	(111,935)	(39,284)	(151,208)
Beginning balance (in shares) at Jun. 30, 2020	11,229,819
Shares issued under stock-based compensation plans (in shares)	663
Stock-based compensation		25		25
Components of comprehensive income:
Net income			5,809	5,809
Ending balance at Sep. 30, 2020	$ 11	(111,910)	(33,475)	(145,374)
Ending balance (in shares) at Sep. 30, 2020	11,230,482
Beginning balance at Dec. 31, 2020	$ 11	(111,858)	(26,190)	$ (138,037)
Beginning balance (in shares) at Dec. 31, 2020	11,230,482			11,230,482
Stock-based compensation		214		$ 214
Stock option exercises		22		22
Stock option exercises (in shares)	8,512
Components of comprehensive income:
Net income			15,268	15,268
Ending balance at Sep. 30, 2021	$ 11	(111,622)	(10,922)	$ (122,533)
Ending balance (in shares) at Sep. 30, 2021	11,238,994			11,238,994
Beginning balance at Jun. 30, 2021	$ 11	(111,726)	(17,548)	$ (129,263)
Beginning balance (in shares) at Jun. 30, 2021	11,237,056
Stock-based compensation		116		116
Stock option exercises		(12)		(12)
Stock option exercises (in shares)	1,938
Components of comprehensive income:
Net income			6,626	6,626
Ending balance at Sep. 30, 2021	$ 11	$ (111,622)	$ (10,922)	$ (122,533)
Ending balance (in shares) at Sep. 30, 2021	11,238,994			11,238,994