ALLOWANCE FOR LOAN LOSSES - Text (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses	$ 81,238,000	$ 71,982,000		$ 75,312,000	$ 74,742,000
Increase in allowance for loan losses	9,300,000
Total provision/(credit) for loan losses	31,998,000	(3,564,000)		(2,198,000)
Unfunded loan commitments	6,500,000
Increase in unfunded loan commitments	5,400,000
Shareholders' equity	868,008,000	819,018,000		$ 753,954,000	785,944,000
Total loans	7,104,309,000	6,976,704,000
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loan losses		(20,385,000)
Unfunded loan commitments		1,400,000
Shareholders' equity		13,492,000	[1]		$ 0	[2]
Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 0	$ 0

[1] Impact due to the adoption of ASU 2016-13, Financial Instruments - Credit Losses (Topic 326) (“ASU 2016-13”). See Part II. Item 8. “Financial Statements and Supplementary Data - Note 1: Basis of Presentation and Summary of Significant Accounting Policies.”

[2] Impact due to the adoption of Accounting Standards Update ("ASU") 2016-01, Recognition and Measurements of Financial Assets and Financial Liabilities ("ASU 2016-01") and ASU 2017-12, Targeted Improvements to Accounting for Hedging Activities ("ASU 2017-12"). See Part II. Item 8. “Financial Statements and Supplementary Data - Note 1: Basis of Presentation and Summary of Significant Accounting Policies” in the Company's Annual Report on Form 10-K for the year ended December 31, 2019.