SIGNIFICANT ACCOUNTING POLICIES - Computation and Reconciliation of Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ 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 income (loss) as reported
Net (loss) income, as reported	$ (927)	$ 1,008	$ (5,648)	$ 4,155	$ (5,288)	$ 6,915	$ 17,244	$ 15,170	$ (1,412)	$ 34,041	$ 30,473
Less: Distributed net income available to participating securities									0	(85)	(27)
Less: Undistributed net income available to participating securities									0	(582)	(666)
Numerator for basic net (loss) income per share:									(1,412)	33,374	29,780
Add: Undistributed net income allocated to participating securities									0	582	666
Less: Undistributed net income reallocated to participating securities									0	(579)	(662)
Numerator for diluted net (loss) income per share:									$ (1,412)	$ 33,377	$ 29,784
Denominator:
Weighted average shares outstanding for basic net (loss) income per share (in shares)									14,790,296	14,579,608	14,529,745
Effect of dilutive securities (in shares)									0	75,742	90,890
Weighted average shares outstanding for diluted net (loss) income per share (in shares)									14,790,296	14,655,350	14,620,635
Net (loss) income per share
Basic (in dollars per share)	$ (0.06)	$ 0.07	$ (0.38)	$ 0.28	$ (0.36)	$ 0.47	$ 1.17	$ 1.02	$ (0.10)	$ 2.29	$ 2.05
Diluted (in dollars per share)	$ (0.06)	$ 0.07	$ (0.38)	$ 0.28	$ (0.36)	$ 0.46	$ 1.15	$ 1.01	$ (0.10)	$ 2.28	$ 2.04