SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Derivative Instruments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Minimum
Derivative [Line Items]
Period between issuance of a loan commitment and closing and sale of the loan	30 days
Maximum
Derivative [Line Items]
Period between issuance of a loan commitment and closing and sale of the loan	120 days
Level III
Derivative [Line Items]
Interest rate lock commitments	$ 43,679,000	$ 38,919,000	$ 35,172,000
Forward Sales Commitments
Derivative [Line Items]
Derivative liability	0	0
Fair value hedge
Derivative [Line Items]
Notional amount	23,000,000.0	30,000,000.0
Carrying Value | Interest rate lock commitment
Derivative [Line Items]
Derivative asset		1,660,000
Carrying Value | Interest rate swap
Derivative [Line Items]
Derivative liability	13,822,000	5,722,000
Derivative asset	13,822,000	5,722,000
Carrying Value | Fair value hedge
Derivative [Line Items]
Derivative liability	2,141,000	1,418,000
Derivative asset	2,215,000	1,770,000
Derivative fair value	100,000	400,000
Estimated Fair Value | Interest rate lock commitment
Derivative [Line Items]
Derivative asset		1,660,000
Estimated Fair Value | Interest rate lock commitment | Level III
Derivative [Line Items]
Derivative asset		1,660,000
Estimated Fair Value | Interest rate swap
Derivative [Line Items]
Derivative liability	13,822,000	5,722,000
Derivative asset	13,822,000	5,722,000
Estimated Fair Value | Interest rate swap | Level III
Derivative [Line Items]
Derivative liability	0	0
Derivative asset	0	0
Estimated Fair Value | Fair value hedge
Derivative [Line Items]
Derivative liability	2,141,000	1,418,000
Derivative asset	2,215,000	1,770,000
Estimated Fair Value | Fair value hedge | Level III
Derivative [Line Items]
Derivative liability	0
Derivative asset	0	0
Interest Rate Lock Commitments | Interest rate lock commitment | Level III
Derivative [Line Items]
Interest rate lock commitments	$ 0	$ 1,660,000	$ 1,750,000