XML 57 R47.htm IDEA: XBRL DOCUMENT
v3.23.2

Allowance for Credit Losses and Credit Quality of Loans, Credit Quality Indicators (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |  |  |
Minimum number of days past due for loans to be considered nonperforming |  |  | 90 days |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | $ 750,183 |  | $ 750,183 |  | $ 1,952,599
2022/2021 | 1,841,436 |  | 1,841,436 |  | 1,615,395
2021/2020 | 1,498,097 |  | 1,498,097 |  | 1,012,149
2020/2019 | 930,442 |  | 930,442 |  | 774,792
2019/2018 | 698,192 |  | 698,192 |  | 518,993
Prior | 1,739,087 |  | 1,739,087 |  | 1,414,638
Revolving Loans Amortized Cost Basis | 854,937 |  | 854,937 |  | 800,156
Revolving Loans Converted to Term | 45,750 |  | 45,750 |  | 61,425
Total | 8,358,124 |  | 8,358,124 |  | 8,150,147
Gross Charge-offs by Loan Class by Vintage [Abstract] |  |  |  |  |
2023 |  |  | (253) |  |
2022 |  |  | (2,922) |  |
2021 |  |  | (4,731) |  |
2020 |  |  | (1,146) |  |
2019 |  |  | (930) |  |
Prior |  |  | (1,017) |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total | (5,149) | $ (4,046) | (10,999) | $ (8,537) |
C&I [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 130,595 |  | 130,595 |  | 297,682
2022/2021 | 288,408 |  | 288,408 |  | 253,483
2021/2020 | 227,937 |  | 227,937 |  | 169,738
2020/2019 | 148,066 |  | 148,066 |  | 94,817
2019/2018 | 79,794 |  | 79,794 |  | 40,593
Prior | 58,223 |  | 58,223 |  | 36,800
Revolving Loans Amortized Cost Basis | 366,033 |  | 366,033 |  | 344,748
Revolving Loans Converted to Term | 11,856 |  | 11,856 |  | 3,296
Total | 1,310,912 |  | 1,310,912 |  | 1,241,157
Gross Charge-offs by Loan Class by Vintage [Abstract] |  |  |  |  |
2023 |  |  | 0 |  |
2022 |  |  | (1) |  |
2021 |  |  | (5) |  |
2020 |  |  | (63) |  |
2019 |  |  | 0 |  |
Prior |  |  | (193) |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total |  |  | (262) |  |
C&I [Member] | Pass [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 129,726 |  | 129,726 |  | 296,562
2022/2021 | 284,195 |  | 284,195 |  | 252,480
2021/2020 | 226,716 |  | 226,716 |  | 164,976
2020/2019 | 143,819 |  | 143,819 |  | 91,497
2019/2018 | 77,298 |  | 77,298 |  | 39,394
Prior | 56,009 |  | 56,009 |  | 32,413
Revolving Loans Amortized Cost Basis | 338,877 |  | 338,877 |  | 327,166
Revolving Loans Converted to Term | 9,668 |  | 9,668 |  | 3,133
Total | 1,266,308 |  | 1,266,308 |  | 1,207,621
C&I [Member] | Special Mention [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 0 |  | 0 |  | 1,044
2022/2021 | 2,440 |  | 2,440 |  | 524
2021/2020 | 421 |  | 421 |  | 4,531
2020/2019 | 3,610 |  | 3,610 |  | 194
2019/2018 | 40 |  | 40 |  | 1,108
Prior | 380 |  | 380 |  | 417
Revolving Loans Amortized Cost Basis | 4,654 |  | 4,654 |  | 5,234
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 11,545 |  | 11,545 |  | 13,052
C&I [Member] | Substandard [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 869 |  | 869 |  | 76
2022/2021 | 1,772 |  | 1,772 |  | 459
2021/2020 | 733 |  | 733 |  | 231
2020/2019 | 587 |  | 587 |  | 3,098
2019/2018 | 2,452 |  | 2,452 |  | 91
Prior | 1,819 |  | 1,819 |  | 3,969
Revolving Loans Amortized Cost Basis | 22,502 |  | 22,502 |  | 12,348
Revolving Loans Converted to Term | 2,188 |  | 2,188 |  | 163
Total | 32,922 |  | 32,922 |  | 20,435
C&I [Member] | Doubtful [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 0 |  | 0 |  | 0
2022/2021 | 1 |  | 1 |  | 20
2021/2020 | 67 |  | 67 |  | 0
2020/2019 | 50 |  | 50 |  | 28
2019/2018 | 4 |  | 4 |  | 0
Prior | 15 |  | 15 |  | 1
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 137 |  | 137 |  | 49
CRE [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 144,657 |  | 144,657 |  | 375,227
2022/2021 | 385,237 |  | 385,237 |  | 466,754
2021/2020 | 462,767 |  | 462,767 |  | 442,196
2020/2019 | 421,626 |  | 421,626 |  | 340,146
2019/2018 | 326,468 |  | 326,468 |  | 223,612
Prior | 757,320 |  | 757,320 |  | 614,625
Revolving Loans Amortized Cost Basis | 244,465 |  | 244,465 |  | 203,126
Revolving Loans Converted to Term | 15,550 |  | 15,550 |  | 29,722
Total | 2,758,090 |  | 2,758,090 |  | 2,695,408
Gross Charge-offs by Loan Class by Vintage [Abstract] |  |  |  |  |
2023 |  |  | 0 |  |
2022 |  |  | 0 |  |
2021 |  |  | 0 |  |
2020 |  |  | 0 |  |
2019 |  |  | (114) |  |
Prior |  |  | 0 |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total |  |  | (114) |  |
CRE [Member] | Pass [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 144,348 |  | 144,348 |  | 374,313
2022/2021 | 382,793 |  | 382,793 |  | 465,990
2021/2020 | 449,149 |  | 449,149 |  | 439,012
2020/2019 | 412,649 |  | 412,649 |  | 333,568
2019/2018 | 313,179 |  | 313,179 |  | 217,141
Prior | 698,047 |  | 698,047 |  | 566,783
Revolving Loans Amortized Cost Basis | 229,150 |  | 229,150 |  | 201,563
Revolving Loans Converted to Term | 15,550 |  | 15,550 |  | 24,735
Total | 2,644,865 |  | 2,644,865 |  | 2,623,105
CRE [Member] | Special Mention [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 0 |  | 0 |  | 605
2022/2021 | 2,251 |  | 2,251 |  | 764
2021/2020 | 6,722 |  | 6,722 |  | 868
2020/2019 | 3,354 |  | 3,354 |  | 2,641
2019/2018 | 10,119 |  | 10,119 |  | 4,649
Prior | 14,216 |  | 14,216 |  | 24,023
Revolving Loans Amortized Cost Basis | 13,768 |  | 13,768 |  | 850
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 50,430 |  | 50,430 |  | 34,400
CRE [Member] | Substandard [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 309 |  | 309 |  | 309
2022/2021 | 193 |  | 193 |  | 0
2021/2020 | 6,896 |  | 6,896 |  | 2,316
2020/2019 | 5,623 |  | 5,623 |  | 3,937
2019/2018 | 3,170 |  | 3,170 |  | 1,822
Prior | 45,057 |  | 45,057 |  | 23,819
Revolving Loans Amortized Cost Basis | 1,547 |  | 1,547 |  | 713
Revolving Loans Converted to Term | 0 |  | 0 |  | 4,987
Total | 62,795 |  | 62,795 |  | 37,903
Auto [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 249,677 |  | 249,677 |  | 489,366
2022/2021 | 418,642 |  | 418,642 |  | 239,745
2021/2020 | 194,620 |  | 194,620 |  | 76,257
2020/2019 | 57,048 |  | 57,048 |  | 100,000
2019/2018 | 69,627 |  | 69,627 |  | 44,277
Prior | 29,488 |  | 29,488 |  | 13,056
Revolving Loans Amortized Cost Basis | 14 |  | 14 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 1,019,116 |  | 1,019,116 |  | 962,701
Gross Charge-offs by Loan Class by Vintage [Abstract] |  |  |  |  |
2023 |  |  | (30) |  |
2022 |  |  | (525) |  |
2021 |  |  | (516) |  |
2020 |  |  | (204) |  |
2019 |  |  | (165) |  |
Prior |  |  | (130) |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total |  |  | (1,570) |  |
Auto [Member] | Performing [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 249,677 |  | 249,677 |  | 488,776
2022/2021 | 418,275 |  | 418,275 |  | 239,090
2021/2020 | 193,855 |  | 193,855 |  | 75,853
2020/2019 | 56,852 |  | 56,852 |  | 99,615
2019/2018 | 69,477 |  | 69,477 |  | 44,061
Prior | 29,327 |  | 29,327 |  | 13,027
Revolving Loans Amortized Cost Basis | 14 |  | 14 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 1,017,477 |  | 1,017,477 |  | 960,422
Auto [Member] | Nonperforming [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 0 |  | 0 |  | 590
2022/2021 | 367 |  | 367 |  | 655
2021/2020 | 765 |  | 765 |  | 404
2020/2019 | 196 |  | 196 |  | 385
2019/2018 | 150 |  | 150 |  | 216
Prior | 161 |  | 161 |  | 29
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 1,639 |  | 1,639 |  | 2,279
Residential Solar [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 129,390 |  | 129,390 |  | 486,262
2022/2021 | 448,024 |  | 448,024 |  | 194,069
2021/2020 | 185,491 |  | 185,491 |  | 74,582
2020/2019 | 69,994 |  | 69,994 |  | 54,687
2019/2018 | 50,490 |  | 50,490 |  | 36,135
Prior | 42,976 |  | 42,976 |  | 11,063
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 926,365 |  | 926,365 |  | 856,798
Gross Charge-offs by Loan Class by Vintage [Abstract] |  |  |  |  |
2023 |  |  | 0 |  |
2022 |  |  | (578) |  |
2021 |  |  | (428) |  |
2020 |  |  | (45) |  |
2019 |  |  | (164) |  |
Prior |  |  | (139) |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total |  |  | (1,354) |  |
Residential Solar [Member] | Performing [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 129,390 |  | 129,390 |  | 485,942
2022/2021 | 447,725 |  | 447,725 |  | 193,971
2021/2020 | 185,410 |  | 185,410 |  | 74,532
2020/2019 | 69,994 |  | 69,994 |  | 54,662
2019/2018 | 50,419 |  | 50,419 |  | 36,119
Prior | 42,927 |  | 42,927 |  | 11,019
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 925,865 |  | 925,865 |  | 856,245
Residential Solar [Member] | Nonperforming [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 0 |  | 0 |  | 320
2022/2021 | 299 |  | 299 |  | 98
2021/2020 | 81 |  | 81 |  | 50
2020/2019 | 0 |  | 0 |  | 25
2019/2018 | 71 |  | 71 |  | 16
Prior | 49 |  | 49 |  | 44
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total | 500 |  | 500 |  | 553
Other Consumer [Member] |  |  |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |  |  |
Overdrawn deposit related to gross charge-offs reported as 2022 originations |  |  | 200 |  |
Overdrawn deposit related to gross charge-offs reported as 2023 originations |  |  | 200 |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 7,876 |  | 7,876 |  | 52,783
2022/2021 | 36,471 |  | 36,471 |  | 111,462
2021/2020 | 82,150 |  | 82,150 |  | 36,807
2020/2019 | 27,611 |  | 27,611 |  | 27,630
2019/2018 | 20,105 |  | 20,105 |  | 15,593
Prior | 22,199 |  | 22,199 |  | 15,822
Revolving Loans Amortized Cost Basis | 17,428 |  | 17,428 |  | 19,226
Revolving Loans Converted to Term | 43 |  | 43 |  | 265
Total | 213,883 |  | 213,883 |  | 279,588
Gross Charge-offs by Loan Class by Vintage [Abstract] |  |  |  |  |
2023 |  |  | (223) |  |
2022 |  |  | (1,818) |  |
2021 |  |  | (3,700) |  |
2020 |  |  | (834) |  |
2019 |  |  | (487) |  |
Prior |  |  | (193) |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total |  |  | (7,255) |  |
Other Consumer [Member] | Performing [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 7,876 |  | 7,876 |  | 52,545
2022/2021 | 36,057 |  | 36,057 |  | 110,624
2021/2020 | 81,241 |  | 81,241 |  | 36,412
2020/2019 | 27,518 |  | 27,518 |  | 27,383
2019/2018 | 20,021 |  | 20,021 |  | 15,536
Prior | 21,995 |  | 21,995 |  | 15,735
Revolving Loans Amortized Cost Basis | 17,423 |  | 17,423 |  | 19,218
Revolving Loans Converted to Term | 14 |  | 14 |  | 250
Total | 212,145 |  | 212,145 |  | 277,703
Other Consumer [Member] | Nonperforming [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 0 |  | 0 |  | 238
2022/2021 | 414 |  | 414 |  | 838
2021/2020 | 909 |  | 909 |  | 395
2020/2019 | 93 |  | 93 |  | 247
2019/2018 | 84 |  | 84 |  | 57
Prior | 204 |  | 204 |  | 87
Revolving Loans Amortized Cost Basis | 5 |  | 5 |  | 8
Revolving Loans Converted to Term | 29 |  | 29 |  | 15
Total | 1,738 |  | 1,738 |  | 1,885
Residential [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 87,988 |  | 87,988 |  | 251,279
2022/2021 | 264,654 |  | 264,654 |  | 349,882
2021/2020 | 345,132 |  | 345,132 |  | 212,569
2020/2019 | 206,097 |  | 206,097 |  | 157,512
2019/2018 | 151,708 |  | 151,708 |  | 158,783
Prior | 828,881 |  | 828,881 |  | 723,272
Revolving Loans Amortized Cost Basis | 226,997 |  | 226,997 |  | 233,056
Revolving Loans Converted to Term | 18,301 |  | 18,301 |  | 28,142
Total | 2,129,758 |  | 2,129,758 |  | 2,114,495
Gross Charge-offs by Loan Class by Vintage [Abstract] |  |  |  |  |
2023 |  |  | 0 |  |
2022 |  |  | 0 |  |
2021 |  |  | (82) |  |
2020 |  |  | 0 |  |
2019 |  |  | 0 |  |
Prior |  |  | (362) |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total | (105) | $ (90) | (444) | $ (402) |
Residential [Member] | Performing [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 87,959 |  | 87,959 |  | 251,012
2022/2021 | 264,222 |  | 264,222 |  | 349,498
2021/2020 | 344,895 |  | 344,895 |  | 212,161
2020/2019 | 205,768 |  | 205,768 |  | 156,957
2019/2018 | 151,242 |  | 151,242 |  | 157,755
Prior | 822,754 |  | 822,754 |  | 717,621
Revolving Loans Amortized Cost Basis | 226,997 |  | 226,997 |  | 233,056
Revolving Loans Converted to Term | 18,301 |  | 18,301 |  | 28,122
Total | 2,122,138 |  | 2,122,138 |  | 2,106,182
Residential [Member] | Nonperforming [Member] |  |  |  |  |
Credit Quality by Loan Class by Vintage [Abstract] |  |  |  |  |
2023/2022 | 29 |  | 29 |  | 267
2022/2021 | 432 |  | 432 |  | 384
2021/2020 | 237 |  | 237 |  | 408
2020/2019 | 329 |  | 329 |  | 555
2019/2018 | 466 |  | 466 |  | 1,028
Prior | 6,127 |  | 6,127 |  | 5,651
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 20
Total | $ 7,620 |  | $ 7,620 |  | $ 8,313

X
- Definition Amount of overdrawn deposit included in gross write-off, originated in current fiscal year. + References No definition available. + Details
Name: | nbtb_FinancingReceivableYearOneOriginatedCurrentFiscalYearOverdrawnDeposit
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of overdrawn deposit included in gross writeoff, originated in fiscal year before current fiscal year. + References No definition available. + Details
Name: | nbtb_FinancingReceivableYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearOverdrawnDeposit
Namespace Prefix: | nbtb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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
Name: | nbtb_ThresholdPeriodPastDueForLoansToBeConsideredNonperforming
Namespace Prefix: | nbtb_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossWriteoffByOriginationYearAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of writeoff of financing receivable, charged against allowance for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 11B -Subparagraph (c)(3) -SubTopic 10 -Topic 310 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-11B + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_FinancingReceivableBeforeAllowanceForCreditLossByOriginationYearAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortized cost of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable originated in current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of writeoff of financing receivable originated more than five years before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-5 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortized cost of financing receivable that can be withdrawn, repaid, and redrawn. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableRevolving
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of revolving financing receivable converted to term loan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6A + Details
Name: | us-gaap_FinancingReceivableRevolvingConvertedToTermLoan
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of writeoff of revolving financing receivable converted to term loan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6A + Details
Name: | us-gaap_FinancingReceivableRevolvingConvertedToTermLoanWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of writeoff of financing receivable that can be withdrawn, repaid, and redrawn. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableRevolvingWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of writeoff of financing receivable originated four years before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of writeoff of financing receivable originated three years before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of writeoff of financing receivable originated in current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableYearOneOriginatedCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of writeoff of financing receivable originated two years before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of writeoff of financing receivable originated in fiscal year before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 80 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-80 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479344/326-20-45-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(3)(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (a) -Subparagraph (1) -Publisher SEC Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (a) -Subparagraph (2) -Publisher SEC Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Name Regulation S-K (SK) -Number 229 -Section 1404 -Paragraph (a) -Publisher SEC Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-14 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 7A -SubTopic 10 -Topic 310 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-7A Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-5 + Details
Name: | us-gaap_NotesReceivableGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nbtb_CommercialAndIndustrialMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_PassMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_DoubtfulMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nbtb_AutoFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nbtb_ResidentialSolarMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nbtb_ConsumerFinancingReceivableExcludingAutoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |