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LOANS - Allowance for Credit Losses (Details) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 USD ($) | Sep. 30, 2020 USD ($) | Sep. 30, 2021 USD ($) | Sep. 30, 2020 USD ($) | Dec. 31, 2020 USD ($)
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period | $ 51,750 | $ 64,437 | $ 60,869 | $ 49,911 | $ 49,911
Charge-offs | (2,703) | (2,720) | (5,775) |  |
Recoveries | 1,353 | 1,463 | 4,636 |  |
Steuben acquisition |  | 1,782 |  |  |
Provision | (901) |  | (10,231) |  |
Balance, end of period | 49,499 | 64,962 | 49,499 | 64,962 | 60,869
Liabilities for off-balance-sheet credit exposures [Roll Forward] |  |  |  |  |
Beginning balance | 762 | 1,452 | 1,489 | 0 | 0
Charge-offs | 0 | 0 | 0 |  |
Recoveries | 0 | 0 | 0 |  |
Steuben acquisition |  | 163 |  |  |
Provision | (43) |  | (770) |  |
Ending balance | 719 | 1,615 | 719 | 1,615 | 1,489
Total allowance for credit losses [Roll Forward] |  |  |  |  |
Beginning balance | 52,512 | 65,889 | 62,358 | 49,911 | 49,911
Charge-offs | (2,703) | (2,720) | (5,775) |  |
Recoveries | 1,353 | 1,463 | 4,636 |  |
Steuben acquisition |  | 1,945 |  |  |
Provision | (944) |  | (11,001) |  |
Ending balance | $ 50,218 | 66,577 | $ 50,218 | 66,577 | $ 62,358
Allowance for Credit Losses |  |  |  |  |
Allowance for credit losses to total loans ratio | 0.68 |  | 0.68 |  |
Basis points lower level |  |  | 19 |  | 14
Accrued interest and fees receivable | $ 18,200 |  | $ 18,200 |  |
Minimum [Member] | COVID-19 [Member] |  |  |  |  |
Allowance for Credit Losses |  |  |  |  |
Percentage of peak unemployment |  |  | 2.90% |  |
Maximum [Member] | COVID-19 [Member] |  |  |  |  |
Allowance for Credit Losses |  |  |  |  |
Percentage of peak unemployment |  |  | 9.10% |  |
Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 51,268 | $ 51,268
Charge-offs |  |  |  | (7,861) |
Recoveries |  |  |  | 4,144 |
Steuben acquisition |  |  |  | 3,662 |
Provision |  |  |  | 13,749 |
Balance, end of period |  | 64,962 |  | 64,962 |
Liabilities for off-balance-sheet credit exposures [Roll Forward] |  |  |  |  |
Beginning balance |  |  |  | 1,185 | 1,185
Charge-offs |  |  |  | 0 |
Recoveries |  |  |  | 0 |
Steuben acquisition |  |  |  | 67 |
Provision |  |  |  | 363 |
Ending balance |  | 1,615 |  | 1,615 |
Total allowance for credit losses [Roll Forward] |  |  |  |  |
Beginning balance |  |  |  | 52,453 | 52,453
Charge-offs |  |  |  | (7,861) |
Recoveries |  |  |  | 4,144 |
Steuben acquisition |  |  |  | 3,729 |
Provision |  |  |  | 14,112 |
Ending balance |  | 66,577 |  | 66,577 |
Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 1,357 | 1,357
Liabilities for off-balance-sheet credit exposures [Roll Forward] |  |  |  |  |
Beginning balance |  |  |  | 1,185 | 1,185
Total allowance for credit losses [Roll Forward] |  |  |  |  |
Beginning balance |  |  |  | 2,542 | 2,542
Acquired Impaired Loans [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 163 | 163
Acquired Impaired Loans [Member] | Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 0 | 0
Charge-offs |  |  |  | 0 |
Recoveries |  |  |  | 0 |
Steuben acquisition |  |  |  | 0 |
Provision |  |  |  | 0 |
Balance, end of period |  | 0 |  | 0 |
Acquired Impaired Loans [Member] | Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | (163) | (163)
Acquired Impaired [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period | 1,885 | 3,561 | $ 1,882 | 0 | 0
Charge-offs | 0 | (91) | 0 |  |
Recoveries | 35 | 32 | 95 |  |
Steuben acquisition |  | 45 |  |  |
Provision | 373 |  | 316 |  |
Balance, end of period | 2,293 | 3,547 | 2,293 | 3,547 | 1,882
Acquired Impaired [Member] | Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 3,072 | 3,072
Charge-offs |  |  |  | (91) |
Recoveries |  |  |  | 80 |
Steuben acquisition |  |  |  | 528 |
Provision |  |  |  | (42) |
Balance, end of period |  | 3,547 |  | 3,547 |
Acquired Impaired [Member] | Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 3,072 | 3,072
Commercial Portfolio Segment [Member] | Business Lending [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period | 23,417 | 24,204 | 28,190 | 19,426 | 19,426
Charge-offs | (872) | (736) | (925) |  |
Recoveries | 169 | 67 | 491 |  |
Steuben acquisition |  | 3,539 |  |  |
Provision | (2,688) |  | (7,730) |  |
Balance, end of period | 20,026 | 27,074 | 20,026 | 27,074 | 28,190
Commercial Portfolio Segment [Member] | Business Lending [Member] | Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 19,714 | 19,714
Charge-offs |  |  |  | (919) |
Recoveries |  |  |  | 289 |
Steuben acquisition |  |  |  | 2,483 |
Provision |  |  |  | 5,507 |
Balance, end of period |  | 27,074 |  | 27,074 |
Commercial Portfolio Segment [Member] | Business Lending [Member] | Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 288 | 288
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period | 10,001 | 13,088 | 10,672 | 10,269 | 10,269
Charge-offs | (127) | (248) | (369) |  |
Recoveries | 3 | 23 | 22 |  |
Steuben acquisition |  | 599 |  |  |
Provision | (132) |  | (580) |  |
Balance, end of period | 9,745 | 12,264 | 9,745 | 12,264 | 10,672
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 9,218 | 9,218
Charge-offs |  |  |  | (668) |
Recoveries |  |  |  | 67 |
Steuben acquisition |  |  |  | 146 |
Provision |  |  |  | 3,501 |
Balance, end of period |  | 12,264 |  | 12,264 |
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | (1,051) | (1,051)
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period | 11,103 | 15,866 | 13,696 | 13,712 | 13,712
Charge-offs | (1,365) | (1,281) | (3,514) |  |
Recoveries | 973 | 1,111 | 3,402 |  |
Steuben acquisition |  | 963 |  |  |
Provision | 1,334 |  | (1,539) |  |
Balance, end of period | 12,045 | 14,733 | 12,045 | 14,733 | 13,696
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 12,715 | 12,715
Charge-offs |  |  |  | (4,791) |
Recoveries |  |  |  | 3,107 |
Steuben acquisition |  |  |  | 183 |
Provision |  |  |  | 3,519 |
Balance, end of period |  | 14,733 |  | 14,733 |
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | (997) | (997)
Consumer Portfolio Segment [Member] | Consumer Direct [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period | 2,548 | 4,028 | 3,207 | 3,255 | 3,255
Charge-offs | (309) | (340) | (822) |  |
Recoveries | 163 | 225 | 607 |  |
Steuben acquisition |  | 120 |  |  |
Provision | 268 |  | (322) |  |
Balance, end of period | 2,670 | 3,793 | 2,670 | 3,793 | 3,207
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 2,612 | 2,612
Charge-offs |  |  |  | (1,214) |
Recoveries |  |  |  | 578 |
Steuben acquisition |  |  |  | 87 |
Provision |  |  |  | 1,730 |
Balance, end of period |  | 3,793 |  | 3,793 |
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | (643) | (643)
Consumer Portfolio Segment [Member] | Home Equity [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period | 1,796 | 2,690 | 2,222 | 2,129 | 2,129
Charge-offs | (30) | (24) | (145) |  |
Recoveries | 10 | 5 | 19 |  |
Steuben acquisition |  | 124 |  |  |
Provision | (56) |  | (376) |  |
Balance, end of period | 1,720 | 2,547 | 1,720 | 2,547 | 2,222
Consumer Portfolio Segment [Member] | Home Equity [Member] | Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 2,937 | 2,937
Charge-offs |  |  |  | (178) |
Recoveries |  |  |  | 23 |
Steuben acquisition |  |  |  | 235 |
Provision |  |  |  | (470) |
Balance, end of period |  | 2,547 |  | 2,547 |
Consumer Portfolio Segment [Member] | Home Equity [Member] | Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 808 | 808
Unallocated Financing Receivables [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period | 1,000 | 1,000 | 1,000 | 957 | 957
Charge-offs | 0 | 0 | 0 |  |
Recoveries | 0 | 0 | 0 |  |
Steuben acquisition |  | 4 |  |  |
Provision | 0 |  | 0 |  |
Balance, end of period | $ 1,000 | 1,004 | $ 1,000 | 1,004 | 1,000
Unallocated Financing Receivables [Member] | Topic ASC 326 [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | 1,000 | 1,000
Charge-offs |  |  |  | 0 |
Recoveries |  |  |  | 0 |
Steuben acquisition |  |  |  | 0 |
Provision |  |  |  | 4 |
Balance, end of period |  | $ 1,004 |  | 1,004 |
Unallocated Financing Receivables [Member] | Topic ASC 326 [Member] | Cumulative Effect Adjustment [Member] |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Balance, beginning of period |  |  |  | $ 43 | $ 43

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