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LOANS - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for loan losses [Roll Forward]
Balance, beginning of period	$ 49,911	$ 49,284
Charge-offs		(13,727)
Recoveries		5,924
Provision	14,212	8,430	$ 10,837
Balance, end of period	60,869	49,911	49,284
Acquired Deteriorated
Allowance for loan losses [Roll Forward]
Balance, beginning of period	0
Balance, end of period		0
Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	10,269
Balance, end of period		10,269
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	10,269	10,124
Charge-offs		(1,372)
Recoveries		60
Provision		1,457
Balance, end of period		10,269	10,124
Commercial Portfolio Segment [Member] | Business Lending [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	19,426	18,522
Charge-offs		(2,334)
Recoveries		826
Provision		2,412
Balance, end of period		19,426	18,522
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	13,712	14,366
Charge-offs		(7,631)
Recoveries		4,180
Provision		2,797
Balance, end of period		13,712	14,366
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	3,255	3,095
Charge-offs		(1,945)
Recoveries		710
Provision		1,395
Balance, end of period		3,255	3,095
Consumer Portfolio Segment [Member] | Home Equity [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	2,129	2,144
Charge-offs		(445)
Recoveries		148
Provision		282
Balance, end of period		2,129	2,144
Unallocated Financing Receivables [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	957	1,000
Charge-offs		0
Recoveries		0
Provision		(43)
Balance, end of period		957	$ 1,000
ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	51,268
Charge-offs	(10,664)
Recoveries	5,689
Provision	10,914
Balance, end of period	60,869	51,268
ASU 2016-13 [Member] | Acquired Deteriorated
Allowance for loan losses [Roll Forward]
Balance, beginning of period	3,072
Charge-offs	(91)
Recoveries	440
Provision	(2,207)
Balance, end of period	1,882	3,072
ASU 2016-13 [Member] | Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	9,218
Charge-offs	(862)
Recoveries	130
Provision	2,040
Balance, end of period	10,672	9,218
ASU 2016-13 [Member] | Commercial Portfolio Segment [Member] | Business Lending [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	19,714
Charge-offs	(1,497)
Recoveries	356
Provision	7,274
Balance, end of period	28,190	19,714
ASU 2016-13 [Member] | Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	12,715
Charge-offs	(6,382)
Recoveries	3,992
Provision	3,188
Balance, end of period	13,696	12,715
ASU 2016-13 [Member] | Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	2,612
Charge-offs	(1,633)
Recoveries	743
Provision	1,398
Balance, end of period	3,207	2,612
ASU 2016-13 [Member] | Consumer Portfolio Segment [Member] | Home Equity [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	2,937
Charge-offs	(199)
Recoveries	28
Provision	(779)
Balance, end of period	2,222	2,937
ASU 2016-13 [Member] | Unallocated Financing Receivables [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	1,000
Charge-offs	0
Recoveries	0
Provision	0
Balance, end of period	$ 1,000	$ 1,000

X

- Definition

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

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
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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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- Definition

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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