SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Earnings Per Share (Details) - USD ($)	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	Dec. 31, 2018
Basic earnings per share computation [Abstract]
Net income applicable to common stock	$ 7,227,000	$ 8,007,000	$ 5,338,000	$ 4,531,000	$ 5,043,000	$ 5,196,000	$ 4,846,000	$ 4,405,000	$ 25,103,000	$ 19,490,000	$ 18,034,000
Weighted average common shares outstanding (in shares)									3,805,682	3,559,150	3,577,992
Earnings per share - basic (in dollars per share)	$ 1.85	$ 2.04	$ 1.39	$ 1.27	$ 1.42	$ 1.46	$ 1.36	$ 1.24	$ 6.60	$ 5.48	$ 5.04
Diluted earnings per share computation [Abstract]
Net income applicable to common stock	$ 7,227,000	$ 8,007,000	$ 5,338,000	$ 4,531,000	$ 5,043,000	$ 5,196,000	$ 4,846,000	$ 4,405,000	$ 25,103,000	$ 19,490,000	$ 18,034,000
Weighted average common shares outstanding for basic earnings per share (in shares)									3,805,682	3,559,150	3,577,992
Add: Dilutive effects of restricted stock (in shares)									1,841	2,096	1,988
Weighted average common shares outstanding for dilutive earnings per share (in shares)									3,807,523	3,561,246	3,579,980
Earnings per share - dilutive (in dollars per share)	$ 1.85	$ 2.04	$ 1.39	$ 1.27	$ 1.42	$ 1.46	$ 1.36	$ 1.24	$ 6.59	$ 5.47	$ 5.04
Restricted Stock [Member]
Antidilutive Securities [Abstract]
Antidilutive restricted stock excluded from net income per share calculations (in shares)									4,302	3,576	3,201
Restricted Stock [Member] | Minimum [Member]
Antidilutive Securities [Abstract]
Antidilutive stock share price range (in dollars per share)									$ 58.37	$ 52.44	$ 47.81
Restricted Stock [Member] | Maximum [Member]
Antidilutive Securities [Abstract]
Antidilutive stock share price range (in dollars per share)									$ 62.93	$ 62.93	$ 61.04