DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net (loss)/income	$ (3,635)	$ 434	$ (12,336)	$ (7,011)	$ (4,835)	$ 3,895	$ 6,585	$ 449	$ (22,548)	$ 6,094	$ 15,494
Net income allocated to restricted stock, Basic										(97)	(154)
Net income allocated to restricted stock, Diluted										(97)	(154)
Net income/(loss) allocated to common shares, Basic									(22,548)	5,997	15,340
Net income/(loss) allocated to common shares, Diluted									$ (22,548)	$ 5,997	$ 15,340
Basic Weighted-Average Shares Outstanding									11,964	11,841	11,677
Dilutive effect of stock options and ESPP										103	95
Dilutive effect of Notes										96
Diluted Weighted-Average Shares Outstanding									11,964	12,040	11,772
Basic earnings/(loss) per share	$ (0.30)	$ 0.04	$ (1.03)	$ (0.59)	$ (0.41)	$ 0.32	$ 0.55	$ 0.04	$ (1.88)	$ 0.51	$ 1.31
Earnings/(Loss) Per Share, Diluted	$ (0.30)	$ 0.04	$ (1.03)	$ (0.59)	$ (0.41)	$ 0.32	$ 0.53	$ 0.04	$ (1.88)	$ 0.50	$ 1.30
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount									1,300	3,000	4,400
Convertible Senior Notes [Member]
Stated interest rate (as a percent)					3.00%					3.00%