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LOANS, Loan Summary (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 6,361,300		$ 4,948,562
Allowance for loan losses	(47,451)	$ (47,096)	(47,233)	$ (46,526)	$ (45,596)	$ (45,401)
Net loans	6,313,849		4,901,329
Credit impaired acquired loans, total balance due	21,700		6,600
Accretable discount related to credit impaired acquired loans [Roll forward]
Beginning Balance	498
Accretion recognized, year-to-date	(264)
Net reclassification to accretable from non-accretable	117
Merchants acquisition	769
Ending Balance	$ 1,120
Consumer Mortgage [Member] | Minimum [Member]
Loans receivable, net [Abstract]
Typical contract term	10 years
Consumer Mortgage [Member] | Maximum [Member]
Loans receivable, net [Abstract]
Typical contract term	30 years
Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 2,479,152		1,490,076
Home Equity [Member] | Maximum [Member]
Loans receivable, net [Abstract]
Typical contract term	30 years
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 2,211,412		1,819,701
Allowance for loan losses	(10,197)	(10,149)	(10,094)	(9,853)	(10,148)	(10,198)
Commercial Portfolio Segment [Member] | Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	2,479,152		1,490,076
Allowance for loan losses	(17,230)	(16,857)	(17,220)	(16,949)	(16,695)	(15,749)
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	1,057,664		1,044,972
Allowance for loan losses	(13,918)	(13,996)	(13,782)	(13,215)	(12,334)	(12,422)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	185,589		191,815
Allowance for loan losses	(2,945)	(2,852)	(2,979)	(3,020)	(2,875)	(2,997)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	427,483		401,998
Allowance for loan losses	$ (2,242)	$ (2,359)	$ (2,399)	$ (2,500)	$ (2,580)	$ (2,666)

X

- Definition

The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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- Definition

The typical original contract term of financial receivable, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

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Amount of accretion recognized for the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities, with evidence of deterioration of credit quality.

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Amount of additions to the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

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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 increase of reclassification from nonaccretable difference to the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

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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 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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