EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
EARNINGS PER SHARE
Net income	$ 13,427	$ 8,365	$ 35,890	$ 18,599
Basic
Weighted average basic shares outstanding	21,928	21,774	21,866	21,750
Earnings per share (in dollars per share)	$ 0.61	$ 0.38	$ 1.64	$ 0.86
Diluted
Dilutive effect of stock-based awards (in shares)	171	157	161	143
Weighted average diluted shares outstanding	22,099	21,931	22,027	21,893
Earnings per share (in dollars per share)	$ 0.61	$ 0.38	$ 1.63	$ 0.85
Anti-dilutive shares excluded from calculation	16	117	56	115