Ratio of allowance for credit losses to total loans.

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Represents the basis points of total loans ratio that are lower than level.

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Amount that has been written off for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of recovery of off-balance sheet credit exposure which had previously been fully or partially written-off. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Percentage of peak unemployment due to decrease in economic activity.

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss, excluding acquisition-related provision for credit losses based on assessment of uncollectible from the counterparty to reduce the account to their net realizable value.

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For an unclassified balance sheet, the amount of fees and other revenue, excluding investment income receivable, earned but not yet received, which were recognized in conformity with revenue recognition criteria based on estimates or specific contractual terms.

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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of increase in allowance for credit loss on financing receivable from recovery.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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Amount of expense related to estimated loss from loan and lease transactions.

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LOANS - Allowance for Credit Losses (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Allowance for loan losses [Roll Forward]
Balance, beginning of period	$ 60,869	$ 49,911	$ 49,911
Charge-offs	(1,966)
Recoveries	1,585
Provision	(5,419)
Balance, end of period	55,069		60,869
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance	1,489	0	0
Charge-offs	0
Recoveries	0
Provision	(300)
Ending balance	1,189		1,489
Total allowance for credit losses [Roll Forward]
Beginning balance	62,358	49,911	49,911
Charge-offs	(1,966)
Recoveries	1,585
Provision	(5,719)
Ending balance	$ 56,258		$ 62,358
Allowance for Credit Losses
Allowance for credit losses to total loans ratio	0.75
Basis points lower level	0.06		0.07
Accrued interest and fees receivable	$ 20,900
Minimum [Member] \| COVID-19 [Member]
Allowance for Credit Losses
Percentage of peak unemployment	3.00%
Maximum [Member] \| COVID-19 [Member]
Allowance for Credit Losses
Percentage of peak unemployment	8.00%
ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		51,268	$ 51,268
Charge-offs		(3,047)
Recoveries		1,497
Provision		5,934
Balance, end of period		55,652
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance		1,185	1,185
Charge-offs		0
Recoveries		0
Provision		(340)
Ending balance		845
Total allowance for credit losses [Roll Forward]
Beginning balance		52,453	52,453
Charge-offs		(3,047)
Recoveries		1,497
Provision		5,594
Ending balance		56,497
ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		1,357	1,357
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance		1,185	1,185
Total allowance for credit losses [Roll Forward]
Beginning balance		2,542	2,542
Acquired Impaired Loans [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		163	163
Acquired Impaired Loans [Member] \| ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		0	0
Charge-offs		0
Recoveries		0
Provision		0
Balance, end of period		0
Acquired Impaired Loans [Member] \| ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		(163)	(163)
Acquired Deteriorated
Allowance for loan losses [Roll Forward]
Balance, beginning of period	$ 1,882	0	0
Charge-offs	0
Recoveries	27
Provision	87
Balance, end of period	1,996		1,882
Acquired Deteriorated \| ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		3,072	3,072
Charge-offs		0
Recoveries		0
Provision		(26)
Balance, end of period		3,046
Acquired Deteriorated \| ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		3,072	3,072
Commercial Portfolio Segment [Member] \| Business Lending [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	28,190	19,426	19,426
Charge-offs	(51)
Recoveries	67
Provision	(1,164)
Balance, end of period	27,042		28,190
Commercial Portfolio Segment [Member] \| Business Lending [Member] \| ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		19,714	19,714
Charge-offs		(176)
Recoveries		138
Provision		(187)
Balance, end of period		19,489
Commercial Portfolio Segment [Member] \| Business Lending [Member] \| ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		288	288
Residential Portfolio Segment [Member] \| Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	10,672	10,269	10,269
Charge-offs	(100)
Recoveries	10
Provision	(896)
Balance, end of period	9,686		10,672
Residential Portfolio Segment [Member] \| Consumer Mortgage [Member] \| ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		9,218	9,218
Charge-offs		(186)
Recoveries		8
Provision		3,390
Balance, end of period		12,430
Residential Portfolio Segment [Member] \| Consumer Mortgage [Member] \| ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		(1,051)	(1,051)
Consumer Portfolio Segment [Member] \| Consumer Indirect [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	13,696	13,712	13,712
Charge-offs	(1,399)
Recoveries	1,246
Provision	(2,423)
Balance, end of period	11,120		13,696
Consumer Portfolio Segment [Member] \| Consumer Indirect [Member] \| ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		12,715	12,715
Charge-offs		(2,079)
Recoveries		1,163
Provision		1,895
Balance, end of period		13,694
Consumer Portfolio Segment [Member] \| Consumer Indirect [Member] \| ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		(997)	(997)
Consumer Portfolio Segment [Member] \| Consumer Direct [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	3,207	3,255	3,255
Charge-offs	(318)
Recoveries	231
Provision	(438)
Balance, end of period	2,682		3,207
Consumer Portfolio Segment [Member] \| Consumer Direct [Member] \| ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		2,612	2,612
Charge-offs		(533)
Recoveries		182
Provision		1,476
Balance, end of period		3,737
Consumer Portfolio Segment [Member] \| Consumer Direct [Member] \| ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		(643)	(643)
Consumer Portfolio Segment [Member] \| Home Equity [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	2,222	2,129	2,129
Charge-offs	(98)
Recoveries	4
Provision	(585)
Balance, end of period	1,543		2,222
Consumer Portfolio Segment [Member] \| Home Equity [Member] \| ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		2,937	2,937
Charge-offs		(73)
Recoveries		6
Provision		(386)
Balance, end of period		2,484
Consumer Portfolio Segment [Member] \| Home Equity [Member] \| ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		808	808
Unallocated Financing Receivables [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	1,000	957	957
Charge-offs	0
Recoveries	0
Provision	0
Balance, end of period	$ 1,000		1,000
Unallocated Financing Receivables [Member] \| ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		1,000	1,000
Charge-offs		0
Recoveries		0
Provision		(228)
Balance, end of period		772
Unallocated Financing Receivables [Member] \| ASU 2016-13 [Member] \| Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		$ 43	$ 43