INVESTMENT SECURITIES - Gains (losses) on sales of investments (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Sales of investment securities available-for-sale		$ 54,023,000	$ 31,220,000	$ 2,743,000
Gross gains		948,000	105,000	352,000
Gross losses		34,000	271,000	25,000
Sales of equity investments		4,622,000	5,968,000	0
Gross gains		3,501,000	0	0
Loss on sale of equity securities		0	7,000	0
Holding gain on equity securities		374,000	13,767,000	590,000
Unrealized holding gains on equity securities	$ 13,500,000
Securities held-to-maturity		0	0
Proceeds from sale of held-to-maturity securities		$ 0	$ 0	$ 0