PREMISES AND EQUIPMENT - Lease Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 3,000	$ 3,000	$ 2,800
Lease liabilities	18,400	14,800
Operating lease, liability	18,272	14,600
Finance lease, liability	176	200
Right-of-use assets	17,700	13,500
Operating lease right-of-use asset	17,500	13,200
Finance lease right of use asset	$ 200	$ 300
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilities	us-gaap:OtherLiabilities
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets	us-gaap:OtherAssets
Finance lease, weighted average remaining lease term	2 years 3 months 18 days	2 years 8 months 12 days
Finance lease, weighted average discount rate	2.40%	2.80%
Operating lease lease, weighted average remaining lease term	12 years 10 months 24 days	11 years 9 months 18 days
Operating lease, weighted average discount rate	2.90%	3.50%
Rent expense			$ 2,000