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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LOANS, Loan Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Loans receivable, net
Gross loans, including deferred origination costs	$ 7,458,643		$ 6,890,543
Allowance for credit losses	(64,962)	$ (64,437)	(49,911)	$ (49,423)	$ (49,310)	$ (49,284)
Net loans	7,393,681		6,840,632
Business Lending [Member]
Loans receivable, net
Gross loans, including deferred origination costs			2,775,876
Commercial Portfolio Segment [Member] \| Business Lending [Member]
Loans receivable, net
Gross loans, including deferred origination costs	3,433,565		2,775,876
Allowance for credit losses	(27,074)	(24,204)	(19,426)	(18,055)	(17,769)	(18,522)
Residential Portfolio Segment [Member] \| Consumer Mortgage [Member]
Loans receivable, net
Gross loans, including deferred origination costs	2,410,249		2,430,902
Allowance for credit losses	(12,264)	(13,088)	(10,269)	(10,477)	(10,763)	(10,124)
Consumer Portfolio Segment [Member] \| Consumer Indirect [Member]
Loans receivable, net
Gross loans, including deferred origination costs	1,039,925		1,113,062
Allowance for credit losses	(14,733)	(15,866)	(13,712)	(14,437)	(14,345)	(14,366)
Consumer Portfolio Segment [Member] \| Consumer Direct [Member]
Loans receivable, net
Gross loans, including deferred origination costs	161,639		184,378
Allowance for credit losses	(3,793)	(4,028)	(3,255)	(3,278)	(3,184)	(3,095)
Consumer Portfolio Segment [Member] \| Home Equity [Member]
Loans receivable, net
Gross loans, including deferred origination costs	413,265		386,325
Allowance for credit losses	$ (2,547)	$ (2,690)	$ (2,129)	$ (2,082)	$ (2,103)	$ (2,144)