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LOANS - Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Aged analysis of the company's loans [Abstract] |  |
Nonaccrual | $ 1,500 |
Total loans | 7,415,952 | $ 6,890,543
Interest income on nonaccrual loans | 0 | 0
Legacy Loan [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
90 + days past due and still accruing | 3,922 | 2,707
Nonaccrual | 72,929 | 15,415
Total past due | 111,610 | 48,684
Current | 7,304,342 | 5,401,908
Total loans | 7,415,952 | 5,450,592
Legacy Loan [Member] | Past Due 30 - 89 Days [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total past due | 34,759 | 30,562
Acquired Loans [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
90 + days past due and still accruing |  | 2,719
Nonaccrual |  | 3,420
Total past due |  | 16,429
Acquired impaired |  | 11,797
Current |  | 1,411,725
Total loans |  | 1,439,951
Acquired Loans [Member] | Past Due 30 - 89 Days [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total past due |  | 10,290
Business Lending [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 2,775,876
Business Lending [Member] | Legacy Loan [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 1,856,585
Business Lending [Member] | Acquired Loans [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 919,291
Consumer Mortgage [Member] | Legacy Loan [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 1,996,716
Consumer Mortgage [Member] | Acquired Loans [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 434,186
Consumer Indirect [Member] | Legacy Loan [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 1,107,308
Consumer Indirect [Member] | Acquired Loans [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 5,754
Consumer Direct [Member] | Legacy Loan [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 175,976
Consumer Direct [Member] | Acquired Loans [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 8,402
Home Equity [Member] | Legacy Loan [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 314,007
Home Equity [Member] | Acquired Loans [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans |  | 72,318
Commercial Portfolio Segment [Member] | Business Lending [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans | 3,440,077 | 2,775,876
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 | 59 | 126
Nonaccrual | 55,709 | 3,840
Total past due | 60,664 | 7,902
Current | 3,379,413 | 1,848,683
Total loans | 3,440,077 | 1,856,585
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 | 4,896 | 3,936
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 |  | 2,173
Nonaccrual |  | 570
Total past due |  | 11,261
Acquired impaired |  | 11,797
Current |  | 896,233
Total loans |  | 919,291
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 |  | 8,518
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans | 2,401,499 | 2,430,902
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 | 3,051 | 2,052
Nonaccrual | 14,970 | 10,131
Total past due | 31,257 | 23,173
Current | 2,370,242 | 1,973,543
Total loans | 2,401,499 | 1,996,716
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 | 13,236 | 10,990
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 |  | 277
Nonaccrual |  | 2,386
Total past due |  | 3,553
Acquired impaired |  | 0
Current |  | 430,633
Total loans |  | 434,186
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 |  | 890
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans | 1,021,885 | 1,113,062
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 | 219 | 125
Nonaccrual | 1 | 0
Total past due | 13,381 | 12,798
Current | 1,008,504 | 1,094,510
Total loans | 1,021,885 | 1,107,308
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 | 13,161 | 12,673
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 |  | 31
Nonaccrual |  | 0
Total past due |  | 110
Acquired impaired |  | 0
Current |  | 5,644
Total loans |  | 5,754
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 |  | 79
Consumer Portfolio Segment [Member] | Consumer Direct [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans | 152,657 | 184,378
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 | 28 | 76
Nonaccrual | 3 | 0
Total past due | 1,201 | 1,531
Current | 151,456 | 174,445
Total loans | 152,657 | 175,976
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 | 1,170 | 1,455
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
Nonaccrual |  | 52
Total past due |  | 111
Acquired impaired |  | 0
Current |  | 8,291
Total loans |  | 8,402
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 |  | 59
Consumer Portfolio Segment [Member] | Home Equity [Member] |  |
Aged analysis of the company's loans [Abstract] |  |
Total loans | 399,834 | 386,325
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 | 565 | 328
Nonaccrual | 2,246 | 1,444
Total past due | 5,107 | 3,280
Current | 394,727 | 310,727
Total loans | 399,834 | 314,007
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 | $ 2,296 | 1,508
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 |  | 238
Nonaccrual |  | 412
Total past due |  | 1,394
Acquired impaired |  | 0
Current |  | 70,924
Total loans |  | 72,318
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 |  | $ 744

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. + Details
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- Definition Amount of financing receivable 90 days or more past due and still accruing. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 16 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5111-111524 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 80 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922355-210448 + Details
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