EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income	$ 13,585	$ 12,458	$ 21,017	$ 21,521
Denominator:
Denominator for basic earnings per share	26,761	26,501	26,729	26,500
Dilutive effect of employee stock awards	132	190	150	181
Denominator for diluted earnings per share	26,893	26,691	26,879	26,681
Earnings per share:
Basic	$ 0.51	$ 0.47	$ 0.79	$ 0.81
Diluted	$ 0.51	$ 0.47	$ 0.78	$ 0.81
Additional Disclosure
Employee stock awards excluded from computation		$ 80		$ 92