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Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 | Dec. 31, 2018
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Minimum number of days past due for nonaccrual loan status | 90 days |
Total past due accruing | $ 36,025 | $ 38,067
Nonaccrual | 25,632 | 25,487
Current | 6,828,655 | 6,824,155
Recorded total loans | 6,890,312 | 6,887,709
31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 26,728 | 26,641
61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 5,962 | 6,341
Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 3,335 | 5,085
Commercial Loans [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Recorded total loans | 3,250,482 | 3,222,310
Consumer Loans [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Recorded total loans | 2,249,419 | 2,284,563
Residential Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Recorded total loans | 1,390,411 | 1,380,836
Originated Loans [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 34,489 | 36,515
Nonaccrual | 23,692 | 23,372
Current | 6,519,588 | 6,505,231
Recorded total loans | 6,577,769 | 6,565,118
Originated Loans [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 25,743 | 25,476
Originated Loans [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 5,556 | 5,969
Originated Loans [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 3,190 | 5,070
Originated Loans [Member] | Commercial Loans [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 7,672 | 3,980
Nonaccrual | 11,687 | 12,031
Current | 3,091,020 | 3,062,609
Recorded total loans | 3,110,379 | 3,078,620
Originated Loans [Member] | Commercial Loans [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 7,017 | 3,090
Originated Loans [Member] | Commercial Loans [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 655 | 302
Originated Loans [Member] | Commercial Loans [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 588
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 74 | 909
Nonaccrual | 899 | 1,062
Current | 858,653 | 846,148
Recorded total loans | 859,626 | 848,119
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 74 | 909
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 6,214 | 1,677
Nonaccrual | 4,818 | 4,995
Current | 1,753,079 | 1,734,558
Recorded total loans | 1,764,111 | 1,741,230
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 5,794 | 1,089
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 420 | 0
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 588
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 1,384 | 1,394
Nonaccrual | 5,970 | 5,974
Current | 479,288 | 481,903
Recorded total loans | 486,642 | 489,271
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 1,149 | 1,092
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 235 | 302
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Originated Loans [Member] | Consumer Loans [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 24,531 | 29,770
Nonaccrual | 5,864 | 4,563
Current | 2,189,398 | 2,218,606
Recorded total loans | 2,219,793 | 2,252,939
Originated Loans [Member] | Consumer Loans [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 17,153 | 20,960
Originated Loans [Member] | Consumer Loans [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 4,503 | 5,510
Originated Loans [Member] | Consumer Loans [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 2,875 | 3,300
Originated Loans [Member] | Consumer Loans [Member] | Dealer Finance [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 14,228 | 18,005
Nonaccrual | 2,924 | 1,971
Current | 1,173,956 | 1,196,136
Recorded total loans | 1,191,108 | 1,216,112
Originated Loans [Member] | Consumer Loans [Member] | Dealer Finance [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 11,388 | 14,519
Originated Loans [Member] | Consumer Loans [Member] | Dealer Finance [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 1,962 | 2,300
Originated Loans [Member] | Consumer Loans [Member] | Dealer Finance [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 878 | 1,186
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 6,572 | 6,814
Nonaccrual | 45 | 0
Current | 522,527 | 518,114
Recorded total loans | 529,144 | 524,928
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 3,235 | 3,479
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 1,733 | 1,773
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 1,604 | 1,562
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 3,731 | 4,951
Nonaccrual | 2,895 | 2,592
Current | 492,915 | 504,356
Recorded total loans | 499,541 | 511,899
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 2,530 | 2,962
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 808 | 1,437
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 393 | 552
Originated Loans [Member] | Residential Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 2,286 | 2,765
Nonaccrual | 6,141 | 6,778
Current | 1,239,170 | 1,224,016
Recorded total loans | 1,247,597 | 1,233,559
Originated Loans [Member] | Residential Real Estate [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 1,573 | 1,426
Originated Loans [Member] | Residential Real Estate [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 398 | 157
Originated Loans [Member] | Residential Real Estate [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 315 | 1,182
Acquired Loans [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 1,536 | 1,552
Nonaccrual | 1,940 | 2,115
Current | 309,067 | 318,924
Recorded total loans | 312,543 | 322,591
Acquired Loans [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 985 | 1,165
Acquired Loans [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 406 | 372
Acquired Loans [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 145 | 15
Acquired Loans [Member] | Commercial Loans [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 406 | 754
Nonaccrual | 383 | 390
Current | 139,314 | 142,546
Recorded total loans | 140,103 | 143,690
Acquired Loans [Member] | Commercial Loans [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 121 | 466
Acquired Loans [Member] | Commercial Loans [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 285 | 288
Acquired Loans [Member] | Commercial Loans [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Commercial Loans [Member] | C&I [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Nonaccrual | 0 | 0
Current | 27,166 | 26,124
Recorded total loans | 27,166 | 26,124
Acquired Loans [Member] | Commercial Loans [Member] | C&I [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Commercial Loans [Member] | C&I [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Commercial Loans [Member] | C&I [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Commercial Loans [Member] | CRE [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Nonaccrual | 0 | 0
Current | 80,623 | 84,492
Recorded total loans | 80,623 | 84,492
Acquired Loans [Member] | Commercial Loans [Member] | CRE [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Commercial Loans [Member] | CRE [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Commercial Loans [Member] | CRE [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 406 | 754
Nonaccrual | 383 | 390
Current | 31,525 | 31,930
Recorded total loans | 32,314 | 33,074
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 121 | 466
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 285 | 288
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Consumer Loans [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 78 | 210
Nonaccrual | 219 | 227
Current | 29,329 | 31,187
Recorded total loans | 29,626 | 31,624
Acquired Loans [Member] | Consumer Loans [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 76 | 153
Acquired Loans [Member] | Consumer Loans [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 2 | 42
Acquired Loans [Member] | Consumer Loans [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 15
Acquired Loans [Member] | Consumer Loans [Member] | Dealer Finance [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 2
Nonaccrual | 0 | 0
Current | 3 | 30
Recorded total loans | 3 | 32
Acquired Loans [Member] | Consumer Loans [Member] | Dealer Finance [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 1
Acquired Loans [Member] | Consumer Loans [Member] | Dealer Finance [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 1
Acquired Loans [Member] | Consumer Loans [Member] | Dealer Finance [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 0
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 78 | 208
Nonaccrual | 219 | 227
Current | 29,326 | 31,157
Recorded total loans | 29,623 | 31,592
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 76 | 152
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 2 | 41
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 0 | 15
Acquired Loans [Member] | Residential Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 1,052 | 588
Nonaccrual | 1,338 | 1,498
Current | 140,424 | 145,191
Recorded total loans | 142,814 | 147,277
Acquired Loans [Member] | Residential Real Estate [Member] | 31-60 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 788 | 546
Acquired Loans [Member] | Residential Real Estate [Member] | 61-90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | 119 | 42
Acquired Loans [Member] | Residential Real Estate [Member] | Greater Than 90 Days Past Due Accruing [Member] |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |
Total past due accruing | $ 145 | $ 0

X
- Definition The threshold period past due for a loan to be considered nonperforming, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Financing receivables that are current. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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 + 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://fasb.org/us-gaap/role/ref/legacyRef -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 and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524 + Details
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Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=nbtb_AcquiredLoansMember
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Data Type: | na
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