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LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
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Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | $ 6,227,030 | $ 6,256,757
Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 5,894 | 2,508
Nonaccrual |  | 15,161 | 16,020
Total past due |  | 47,512 | 51,563
Current |  | 4,644,368 | 4,568,100
Total loans |  | 4,691,880 | 4,619,663
Legacy Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 26,457 | 33,035
Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 531 | 204
Nonaccrual |  | 8,078 | 8,720
Total past due |  | 15,452 | 17,167
Acquired impaired | [1] | 8,496 | 10,115
Current |  | 1,511,202 | 1,609,812
Total loans |  | 1,535,150 | 1,637,094
Acquired Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 6,843 | 8,243
Business Lending [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 2,426,086 | 2,424,223
Business Lending [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 1,450,006 | 1,376,599
Business Lending [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 976,080 | 1,047,624
Consumer Mortgage [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 1,765,864 | 1,754,609
Consumer Mortgage [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 446,018 | 465,689
Consumer Indirect [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 990,766 | 991,836
Consumer Indirect [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 17,432 | 20,142
Consumer Direct [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 168,517 | 174,479
Consumer Direct [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 4,515 | 5,450
Home Equity [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 316,727 | 322,140
Home Equity [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 91,105 | 98,189
Commercial Portfolio Segment [Member] | Business Lending [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 2,426,086 | 2,424,223
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 4,069 | 571
Nonaccrual |  | 3,831 | 3,944
Total past due |  | 12,962 | 6,798
Current |  | 1,437,044 | 1,369,801
Total loans |  | 1,450,006 | 1,376,599
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 5,062 | 2,283
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 |  | 3,967 | 4,328
Total past due |  | 8,086 | 8,989
Acquired impaired | [1] | 8,496 | 10,115
Current |  | 959,498 | 1,028,520
Total loans |  | 976,080 | 1,047,624
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 |  | 4,119 | 4,661
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 2,211,882 | 2,220,298
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 1,437 | 1,500
Nonaccrual |  | 10,086 | 10,722
Total past due |  | 21,759 | 25,786
Current |  | 1,744,105 | 1,728,823
Total loans |  | 1,765,864 | 1,754,609
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 10,236 | 13,564
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 |  | 282 | 26
Nonaccrual |  | 2,855 | 3,066
Total past due |  | 5,128 | 5,695
Acquired impaired | [1] | 0 | 0
Current |  | 440,890 | 459,994
Total loans |  | 446,018 | 465,689
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 |  | 1,991 | 2,603
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 1,008,198 | 1,011,978
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 182 | 295
Nonaccrual |  | 5 | 0
Total past due |  | 8,851 | 14,492
Current |  | 981,915 | 977,344
Total loans |  | 990,766 | 991,836
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 8,664 | 14,197
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 |  | 35 | 8
Nonaccrual |  | 0 | 0
Total past due |  | 141 | 253
Acquired impaired | [1] | 0 | 0
Current |  | 17,291 | 19,889
Total loans |  | 17,432 | 20,142
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 |  | 106 | 245
Consumer Portfolio Segment [Member] | Consumer Direct [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 173,032 | 179,929
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 30 | 48
Nonaccrual |  | 0 | 0
Total past due |  | 1,121 | 1,923
Current |  | 167,396 | 172,556
Total loans |  | 168,517 | 174,479
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 1,091 | 1,875
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 |  | 105 | 100
Acquired impaired | [1] | 0 | 0
Current |  | 4,410 | 5,350
Total loans |  | 4,515 | 5,450
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 |  | 105 | 100
Consumer Portfolio Segment [Member] | Home Equity [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 407,832 | 420,329
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 176 | 94
Nonaccrual |  | 1,239 | 1,354
Total past due |  | 2,819 | 2,564
Current |  | 313,908 | 319,576
Total loans |  | 316,727 | 322,140
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 1,404 | 1,116
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 |  | 214 | 170
Nonaccrual |  | 1,256 | 1,326
Total past due |  | 1,992 | 2,130
Acquired impaired | [1] | 0 | 0
Current |  | 89,113 | 96,059
Total loans |  | 91,105 | 98,189
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 |  | $ 522 | $ 634
[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.

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- 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. + Details
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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 + Details
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- Definition Recorded investment in financing receivables that are on nonaccrual status as of 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 7 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524 + Details
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- Definition 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 + Details
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