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Deposits (Tables) | 12 Months Ended
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Dec. 31, 2017
Deposits [Abstract] |
Maturity distribution of time deposits | The following table sets forth the maturity distribution of time deposits:
(In thousands) |  | December 31, 2017 |
Within one year |  | $ | 394,674 |
After one but within two years |  |  | 259,710 |
After two but within three years |  |  | 62,536 |
After three but within four years |  |  | 40,151 |
After four but within five years |  |  | 28,525 |
After five years |  |  | 21,170 |
Total |  | $ | 806,766 |

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- Definition Sets forth the maturity distributions of time deposits (including certificates of deposits, individual retirement accounts and open accounts) held by the entity with with various term disclosure. + References No definition available. + Details
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Namespace Prefix: | nbtb_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
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- References No definition available. + Details
Name: | us-gaap_DepositsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration