Condensed Consolidated Statements of Shareholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Preferred Stock Series C-1 Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning Balance at Dec. 31, 2020	$ (88,087)	$ 3,907	$ 3	$ 984,755	$ (1,076,752)
Beginning Balance (in shares) at Dec. 31, 2020		4,000	27,403,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,116			1,116
Issuance of common stock under 2013 Equity Plan	154			154
Issuance of common stock under 2013 Equity Plan (in shares)			29,000
Issuance of common stock under ESPP	81			81
Issuance of common stock under ESPP (in shares)			17,000
Net income	14,418				14,418
Ending Balance at Mar. 31, 2021	(72,318)	$ 3,907	$ 3	986,106	(1,062,334)
Ending Balance (in shares) at Mar. 31, 2021		4,000	27,449,000
Beginning Balance at Dec. 31, 2020	(88,087)	$ 3,907	$ 3	984,755	(1,076,752)
Beginning Balance (in shares) at Dec. 31, 2020		4,000	27,403,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	18,151
Ending Balance at Jun. 30, 2021	(67,443)	$ 3,907	$ 3	987,248	(1,058,601)
Ending Balance (in shares) at Jun. 30, 2021		4,000	27,482,000
Beginning Balance at Mar. 31, 2021	(72,318)	$ 3,907	$ 3	986,106	(1,062,334)
Beginning Balance (in shares) at Mar. 31, 2021		4,000	27,449,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,024			1,024
Issuance of common stock under 2013 Equity Plan	1			1
Issuance of common stock under ESPP	117			117
Issuance of common stock under ESPP (in shares)			33,000
Net income	3,733				3,733
Ending Balance at Jun. 30, 2021	(67,443)	$ 3,907	$ 3	987,248	(1,058,601)
Ending Balance (in shares) at Jun. 30, 2021		4,000	27,482,000
Beginning Balance at Dec. 31, 2021	(66,738)	$ 3,907	$ 3	986,444	(1,057,092)
Beginning Balance (in shares) at Dec. 31, 2021		4,000	26,784,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,262			1,262
Issuance of common stock under ESPP	159			159
Issuance of common stock under ESPP (in shares)			42,000
Purchases of common stock under stock repurchase plan	(5,179)			(5,179)
Purchases of common stock under Stock Repurchase Plan (in shares)			(1,162,000)
Net income	2				2
Ending Balance at Mar. 31, 2022	(70,494)	$ 3,907	$ 3	982,686	(1,057,090)
Ending Balance (in shares) at Mar. 31, 2022		4,000	25,664,000
Beginning Balance at Dec. 31, 2021	$ (66,738)	$ 3,907	$ 3	986,444	(1,057,092)
Beginning Balance (in shares) at Dec. 31, 2021		4,000	26,784,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under 2013 Equity Plan (in shares)	500
Net income	$ 2,460
Ending Balance at Jun. 30, 2022	(69,468)	$ 3,907	$ 3	981,254	(1,054,632)
Ending Balance (in shares) at Jun. 30, 2022		4,000	24,950,000
Beginning Balance at Mar. 31, 2022	(70,494)	$ 3,907	$ 3	982,686	(1,057,090)
Beginning Balance (in shares) at Mar. 31, 2022		4,000	25,664,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	1,352			1,352
Issuance of common stock under ESPP	101			101
Issuance of common stock under ESPP (in shares)			31,000
Purchases of common stock under stock repurchase plan	(2,885)			(2,885)
Purchases of common stock under Stock Repurchase Plan (in shares)			(745,000)
Net income	2,458				2,458
Ending Balance at Jun. 30, 2022	$ (69,468)	$ 3,907	$ 3	$ 981,254	$ (1,054,632)
Ending Balance (in shares) at Jun. 30, 2022		4,000	24,950,000