EARNINGS PER SHARE - Computation of EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
EARNINGS PER SHARE.
Net income	$ 9,348	$ 12,927
Dividends paid on and earnings allocated to participating securities	(195)	(277)
Income attributable to common stock	$ 9,153	$ 12,650
Weighted average common shares outstanding, including participating securities	19,946	19,926
Weighted average participating securities (in shares)	(414)	(426)
Weighted average common shares outstanding	19,532	19,500
Basic earnings per common share (in dollars per share)	$ 0.47	$ 0.65
Income attributable to common stock	$ 9,153	$ 12,650
Weighted average common shares outstanding	19,532	19,500
Incremental shares from assumed conversions of options and restricted stock units	34	26
Weighted average common and equivalent shares outstanding (in shares)	19,566	19,526
Diluted earnings per common share (in dollars per share)	$ 0.47	$ 0.65