FAIR VALUE (Schedule of Financial Instruments) (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Financial Assets:
Securities available for sale	$ 622,689,000	$ 390,755,000
FHLB and FRB stock	13,709,000	24,068,000
Loans held for sale, at fair value	13,588,000	2,881,000
Loans held for sale, at lower of cost or fair value	18,520,000	14,667,000
Accrued interest receivable	22,495,000	10,494,000
Financial Liabilities:
Short-term borrowings	15,000,000	128,100,000
Paycheck Protection Program Liquidity Facility	177,086,000
Advances from Federal Home Loan Banks	0	105,000,000.0
Federal Home Loan Bank advances	0	105,000,000.0
Carrying Value [Member]
Financial Assets:
Cash and cash equivalents	653,322,000	208,185,000
Securities available for sale	622,689,000	390,755,000
CRA investment fund	15,117,000	10,836,000
FHLB and FRB stock	13,709,000	24,068,000
Loans held for sale, at fair value	13,588,000	2,881,000
Loans held for sale, at lower of cost or fair value	18,520,000	14,667,000
Loans, net of allowance for loan losses	4,305,128,000	4,350,461,000
Accrued interest receivable	22,495,000	10,494,000
Financial Liabilities:
Deposits	4,818,484,000	4,243,511,000
Short-term borrowings	15,000,000	128,100,000
Paycheck Protection Program Liquidity Facility	177,086,000
Advances from Federal Home Loan Banks		105,000,000
Subordinated debt	181,794,000	83,417,000
Accrued interest payable	1,650,000	2,357,000
Federal Home Loan Bank advances		105,000,000
Fair value [Member]
Financial Assets:
Cash and cash equivalents	653,322,000	208,185,000
Securities available for sale	622,689,000	390,755,000
CRA investment fund	15,117,000	10,836,000
Loans held for sale, at fair value	13,588,000	2,881,000
Loans held for sale, at lower of cost or fair value	19,115,000	15,126,000
Loans, net of allowance for loan losses	4,462,243,000	4,268,481,000
Accrued interest receivable	22,495,000	10,494,000
Financial Liabilities:
Deposits	4,826,406,000	4,247,427,000
Short-term borrowings	15,000,000	128,100,000
Paycheck Protection Program Liquidity Facility	177,086,000
Advances from Federal Home Loan Banks		108,354,000
Subordinated debt	183,348,000	86,536,000
Accrued interest payable	1,650,000	2,357,000
Federal Home Loan Bank advances		108,354,000
Fair value [Member] | Quoted Prices in Active Market For Identical Assets (Level 1) [Member]
Financial Assets:
Cash and cash equivalents	653,322,000	208,185,000
CRA investment fund	15,117,000	10,836,000
Financial Liabilities:
Deposits	4,222,370,000	3,528,609,000
Accrued interest payable	150,000	392,000
Fair value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial Assets:
Securities available for sale	622,689,000	390,755,000
Loans held for sale, at fair value	13,588,000	2,881,000
Loans held for sale, at lower of cost or fair value	19,115,000	15,126,000
Accrued interest receivable	1,653,000	1,361,000
Financial Liabilities:
Deposits	604,036,000	718,818,000
Short-term borrowings	15,000,000	128,100,000
Paycheck Protection Program Liquidity Facility	177,086,000
Advances from Federal Home Loan Banks		108,354,000
Accrued interest payable	1,347,000	1,910,000
Federal Home Loan Bank advances		108,354,000
Fair value [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial Assets:
Loans, net of allowance for loan losses	4,462,243,000	4,268,481,000
Accrued interest receivable	20,842,000	9,133,000
Financial Liabilities:
Subordinated debt	183,348,000	86,536,000
Accrued interest payable	153,000	55,000
Not Designated as Hedging Instrument [Member] | Carrying Value [Member]
Financial Assets:
Derivatives	79,529,000	32,381,000
Financial Liabilities:
Derivatives	79,529,000	32,381,000
Not Designated as Hedging Instrument [Member] | Fair value [Member]
Financial Assets:
Derivatives	79,529,000	32,381,000
Financial Liabilities:
Derivatives	79,529,000	32,381,000
Not Designated as Hedging Instrument [Member] | Fair value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial Assets:
Derivatives	79,529,000	32,381,000
Financial Liabilities:
Derivatives	79,529,000	32,381,000
Designated as Hedging Instrument [Member] | Carrying Value [Member]
Financial Assets:
Derivatives		121,000
Financial Liabilities:
Derivatives	9,616,000	3,788,000
Designated as Hedging Instrument [Member] | Fair value [Member]
Financial Assets:
Derivatives		121,000
Financial Liabilities:
Derivatives	9,616,000	3,788,000
Designated as Hedging Instrument [Member] | Fair value [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial Assets:
Derivatives		121,000
Financial Liabilities:
Derivatives	$ 9,616,000	$ 3,788,000