EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
EARNINGS PER SHARE
Net income	$ 12,073	$ 9,171
Dividends paid on and earnings allocated to participating securities	(253)	(178)
Income attributable to common stock	$ 11,820	$ 8,993
Weighted average common shares outstanding, including participating securities	19,834	19,669
Weighted average participating securities (in shares)	(421)	(392)
Weighted average common shares outstanding	19,413	19,277
Basic earnings per common share (in dollars per share)	$ 0.61	$ 0.47
Income attributable to common stock	$ 11,820	$ 8,993
Weighted average common shares outstanding	19,413	19,277
Incremental shares from assumed conversions of options and restricted stock units	25	19
Weighted average common and equivalent shares outstanding (in shares)	19,438	19,296
Diluted earnings per common share (in dollars per share)	$ 0.61	$ 0.47