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LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Dec. 31, 2016
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Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | $ 6,308,720 | $ 4,948,562
Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 1,589 | 1,963
Nonaccrual |  | 15,069 | 16,600
Total past due |  | 53,064 | 50,545
Current |  | 4,515,199 | 4,402,657
Total loans |  | 4,568,263 | 4,453,202
Legacy Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 36,406 | 31,982
Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
90 + days past due and still accruing |  | 272 | 1,113
Nonaccrual |  | 6,441 | 4,019
Total past due |  | 13,247 | 8,439
Acquired impaired | [1] | 13,594 | 5,553
Current |  | 1,713,616 | 481,368
Total loans |  | 1,740,457 | 495,360
Acquired Loans [Member] | Past Due 30 - 89 Days [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total past due |  | 6,534 | 3,307
Consumer Mortgage [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 1,718,875 | 1,659,760
Consumer Mortgage [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 487,652 | 159,941
Business Lending [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 2,458,981 | 1,490,076
Business Lending [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 1,342,436 | 1,277,666
Business Lending [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 1,116,545 | 212,410
Consumer Indirect [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 1,011,298 | 1,014,825
Consumer Indirect [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 23,418 | 30,147
Consumer Direct [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 177,396 | 181,922
Consumer Direct [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 6,502 | 9,893
Home Equity [Member] | Legacy Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 318,258 | 319,029
Home Equity [Member] | Acquired Loans [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 106,340 | 82,969
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 2,206,527 | 1,819,701
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 |  | 1,275 | 1,180
Nonaccrual |  | 10,454 | 11,352
Total past due |  | 23,041 | 23,911
Current |  | 1,695,834 | 1,635,849
Total loans |  | 1,718,875 | 1,659,760
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 |  | 11,312 | 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 |  | 230 | 205
Nonaccrual |  | 3,526 | 2,332
Total past due |  | 5,705 | 4,076
Acquired impaired | [1] | 0 | 0
Current |  | 481,947 | 155,865
Total loans |  | 487,652 | 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 |  | 1,949 | 1,539
Commercial Portfolio Segment [Member] | Business Lending [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 2,458,981 | 1,490,076
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 |  | 79 | 145
Nonaccrual |  | 3,153 | 3,811
Total past due |  | 12,214 | 7,877
Current |  | 1,330,222 | 1,269,789
Total loans |  | 1,342,436 | 1,277,666
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 |  | 8,982 | 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 |  | 1,570 | 1,252
Total past due |  | 5,063 | 1,780
Acquired impaired | [1] | 13,594 | 5,553
Current |  | 1,097,888 | 205,077
Total loans |  | 1,116,545 | 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 |  | 3,493 | 528
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 1,034,716 | 1,044,972
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 |  | 167 | 166
Nonaccrual |  | 0 | 0
Total past due |  | 13,896 | 14,049
Current |  | 997,402 | 1,000,776
Total loans |  | 1,011,298 | 1,014,825
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 |  | 13,729 | 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 |  | 0 | 3
Nonaccrual |  | 0 | 0
Total past due |  | 198 | 234
Acquired impaired | [1] | 0 | 0
Current |  | 23,220 | 29,913
Total loans |  | 23,418 | 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 |  | 198 | 231
Consumer Portfolio Segment [Member] | Consumer Direct [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 183,898 | 191,815
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 |  | 67 | 58
Nonaccrual |  | 0 | 0
Total past due |  | 1,573 | 1,607
Current |  | 175,823 | 180,315
Total loans |  | 177,396 | 181,922
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 |  | 1,506 | 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 |  | 2 | 0
Nonaccrual |  | 0 | 0
Total past due |  | 133 | 231
Acquired impaired | [1] | 0 | 0
Current |  | 6,369 | 9,662
Total loans |  | 6,502 | 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 |  | 131 | 231
Consumer Portfolio Segment [Member] | Home Equity [Member] |  |  |
Aged analysis of the company's loans [Abstract] |  |  |
Total loans |  | 424,598 | 401,998
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 |  | 1 | 414
Nonaccrual |  | 1,462 | 1,437
Total past due |  | 2,340 | 3,101
Current |  | 315,918 | 315,928
Total loans |  | 318,258 | 319,029
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 |  | 877 | 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 |  | 40 | 905
Nonaccrual |  | 1,345 | 435
Total past due |  | 2,148 | 2,118
Acquired impaired | [1] | 0 | 0
Current |  | 104,192 | 80,851
Total loans |  | 106,340 | 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 |  | $ 763 | $ 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.

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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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