LOANS, Acquired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Credit impaired acquired loans [Abstract]
Outstanding principal balance	$ 16,200	$ 6,936
Carrying amount	11,797	5,446
Credit impaired acquired loans, total balance due	17,100	7,400
Non-impaired acquired loans [Abstract]
Outstanding principal balance	1,448,046	1,271,584
Carrying amount	1,428,154	1,247,691
Total acquired loans [Abstract]
Outstanding principal balance	1,464,246	1,278,520
Carrying amount	1,439,951	1,253,137
Accretable discount related to acquired loans [Roll forward]
Balance at beginning of year	437	976
Kinderhook acquisition	551	0
Accretion recognized	(493)	(783)
Net reclassification from non-accretable to accretable	138	244
Balance at end of year	$ 633	$ 437