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LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Aged analysis of the company's loans [Abstract]
Total loans		$ 6,256,757	$ 4,948,562
Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		2,508	1,963
Nonaccrual		16,020	16,600
Total past due		51,563	50,545
Current		4,568,100	4,402,657
Total loans		4,619,663	4,453,202
Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		33,035	31,982
Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		204	1,113
Nonaccrual		8,720	4,019
Total past due		17,167	8,439
Acquired impaired	[1]	10,115	5,553
Current		1,609,812	481,368
Total loans		1,637,094	495,360
Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		8,243	3,307
Consumer Mortgage [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,754,609	1,659,760
Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		465,689	159,941
Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,424,223	1,490,076
Business Lending [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,376,599	1,277,666
Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,047,624	212,410
Consumer Indirect [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		991,836	1,014,825
Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		20,142	30,147
Consumer Direct [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		174,479	181,922
Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		5,450	9,893
Home Equity [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		322,140	319,029
Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		98,189	82,969
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,220,298	1,819,701
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		1,500	1,180
Nonaccrual		10,722	11,352
Total past due		25,786	23,911
Current		1,728,823	1,635,849
Total loans		1,754,609	1,659,760
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		13,564	11,379
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		26	205
Nonaccrual		3,066	2,332
Total past due		5,695	4,076
Acquired impaired	[1]	0	0
Current		459,994	155,865
Total loans		465,689	159,941
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		2,603	1,539
Commercial Portfolio Segment [Member] | Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,424,223	1,490,076
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		571	145
Nonaccrual		3,944	3,811
Total past due		6,798	7,877
Current		1,369,801	1,269,789
Total loans		1,376,599	1,277,666
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		2,283	3,921
Commercial Portfolio Segment [Member] | Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		0	0
Nonaccrual		4,328	1,252
Total past due		8,989	1,780
Acquired impaired	[1]	10,115	5,553
Current		1,028,520	205,077
Total loans		1,047,624	212,410
Commercial Portfolio Segment [Member] | Business Lending [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		4,661	528
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,011,978	1,044,972
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		295	166
Nonaccrual		0	0
Total past due		14,492	14,049
Current		977,344	1,000,776
Total loans		991,836	1,014,825
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		14,197	13,883
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		8	3
Nonaccrual		0	0
Total past due		253	234
Acquired impaired	[1]	0	0
Current		19,889	29,913
Total loans		20,142	30,147
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		245	231
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Aged analysis of the company's loans [Abstract]
Total loans		179,929	191,815
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		48	58
Nonaccrual		0	0
Total past due		1,923	1,607
Current		172,556	180,315
Total loans		174,479	181,922
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,875	1,549
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		0	0
Nonaccrual		0	0
Total past due		100	231
Acquired impaired	[1]	0	0
Current		5,350	9,662
Total loans		5,450	9,893
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		100	231
Consumer Portfolio Segment [Member] | Home Equity [Member]
Aged analysis of the company's loans [Abstract]
Total loans		420,329	401,998
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		94	414
Nonaccrual		1,354	1,437
Total past due		2,564	3,101
Current		319,576	315,928
Total loans		322,140	319,029
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,116	1,250
Consumer Portfolio Segment [Member] | Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		170	905
Nonaccrual		1,326	435
Total past due		2,130	2,118
Acquired impaired	[1]	0	0
Current		96,059	80,851
Total loans		98,189	82,969
Consumer Portfolio Segment [Member] | Home Equity [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		$ 634	$ 778
[1] Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans.

X

- Definition

Loans acquired after January 1, 2009 that have evidence of deterioration in credit quality since origination and for which it is probable, at acquisition, that the company will be unable to collect all contractually required payments.

+ References

No definition available.

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- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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Financing receivables that are current.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953401-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

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Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953401-111524

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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