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 before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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LOANS, Loan Summary (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 7,528,039		$ 6,890,543
Allowance for credit losses	(64,437)	$ (55,652)	(49,911)	$ (49,310)	$ (49,107)	$ (49,284)
Net loans	7,463,602		6,840,632
Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs			2,775,876
Commercial Portfolio Segment [Member] \| Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	3,455,343		2,775,876
Allowance for credit losses	(24,204)	(19,489)	(19,426)	(17,769)	(18,271)	(18,522)
Residential Portfolio Segment [Member] \| Consumer Mortgage [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	2,428,060		2,430,902
Allowance for credit losses	(13,088)	(12,430)	(10,269)	(10,763)	(10,317)	(10,124)
Consumer Portfolio Segment [Member] \| Consumer Indirect [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	1,056,865		1,113,062
Allowance for credit losses	(15,866)	(13,694)	(13,712)	(14,345)	(14,251)	(14,366)
Consumer Portfolio Segment [Member] \| Consumer Direct [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	169,228		184,378
Allowance for credit losses	(4,028)	(3,737)	(3,255)	(3,184)	(3,056)	(3,095)
Consumer Portfolio Segment [Member] \| Home Equity [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	418,543		386,325
Allowance for credit losses	$ (2,690)	$ (2,484)	$ (2,129)	$ (2,103)	$ (2,067)	$ (2,144)