EARNINGS PER COMMON SHARE (Computation of Basic and Diluted Earnings per 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
Calculations of basic and diluted earnings per share
Number of antidilutive shares not considered in computing diluted earnings per share									0	0
Basic
Net income per consolidated statements of income	$ 11,775	$ 10,783	$ 10,811	$ 6,097	$ 7,863	$ 7,683	$ 6,057	$ 8,531	$ 39,466	$ 30,134
Less: Earnings allocated to participating securities									(344)	(448)
Net income available to common stockholder									$ 39,122	$ 29,686
Weighted average common shares outstanding including participating securities									8,293,677	8,297,478
Less: Weighted average participating securities									(72,248)	(123,336)
Weighted average common shares outstanding									8,221,429	8,174,142
Basic earnings per common share (in dollars per share)	$ 1.42	$ 1.30	$ 1.30	$ 0.73	$ 0.95	$ 0.92	$ 0.73	$ 1.03	$ 4.76	$ 3.63
Diluted
Net income allocated to common shareholders									$ 39,122	$ 29,686
Weighted average common shares outstanding for basic earnings per common share									8,221,429	8,174,142
Average shares and dilutive potential common shares									8,398,444	8,339,141
Diluted earnings per common share (in dollars per share)	$ 1.39	$ 1.27	$ 1.28	$ 0.72	$ 0.93	$ 0.90	$ 0.71	$ 1.01	$ 4.66	$ 3.56
Stock Option
Diluted
Dilutive effects of assumed exercise of stock options/vesting of performance based restricted stock									103,463	125,085
Restricted stock
Calculations of basic and diluted earnings per share
Number of antidilutive shares not considered in computing diluted earnings per share									33,615
Diluted
Dilutive effects of assumed exercise of stock options/vesting of performance based restricted stock									73,552	39,914