SUMMARY OF SIGNIFICANT ACCOUNTING AND REPORTING POLICIES (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) segment banking_offices	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Organization and Basis of Presentation [Abstract]
Number of branches | banking_offices	57
Number of branches in grocery stores | banking_offices	15
Segment Information [Abstract]
Number of reportable segments | segment	1
Cash and Cash Equivalents [Abstract]
Cash on deposit with the Federal Reserve required to meet regulatory reserve and clearing requirements	$ 0	$ 33,800,000
Goodwill and Other Intangible Assets [Abstract]
Goodwill impairment loss	0	0
Cumulative goodwill impairment loss	0	0
Amortization expense of intangible assets	3,617,000	4,418,000	$ 5,213,000
Derivative Instruments and Hedges, Assets [Abstract]
Debt Securities, Held-to-maturity, Allowance for Credit Loss	$ 0
Financing Receivable, Threshold Period Past Due	90 days
Financing Receivable, Threshold Period Past Due, Writeoff	120 days
Core deposit intangible
Goodwill and Other Intangible Assets [Abstract]
Intangible assets, net	$ 6,600,000
Trust relationship intangible
Goodwill and Other Intangible Assets [Abstract]
Intangible assets, net	3,100,000
Core Deposit Intangible and Trust Relationship Intangible [Member]
Goodwill and Other Intangible Assets [Abstract]
Amortization expense of intangible assets	$ 3,500,000	$ 4,300,000	$ 5,100,000
Premises | Minimum
Premises and Equipment [Abstract]
Estimated useful life	15 years
Premises | Maximum
Premises and Equipment [Abstract]
Estimated useful life	40 years
Equipment | Minimum
Premises and Equipment [Abstract]
Estimated useful life	3 years
Equipment | Maximum
Premises and Equipment [Abstract]
Estimated useful life	10 years