Subsequent Event (Details) (Subsequent Event [Member], USD $) In Millions, unless otherwise specified	0 Months Ended
Apr. 17, 2014 SchoolsandHealthcare
Subsequent Event [Member]
Subsequent Event [Line Items]
Percentage of ownership interest sold (in hundredths)	20.00%
Original acquisition price of ownership interest	$ 3
Proceeds from sale of ownership interest	$ 140
Number of schools and healthcare providers	14,000

This line item represents the number of schools and healthcare providers through which affordable financing options for consumers seeking to finance private education and elective medical procedures is provided.

No definition available.

+ Details

Name:	nbtb_NumberOfSchoolsAndHealthcareProviders
Namespace Prefix:	nbtb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

This line item represents the original acquisition price of ownership interest acquired earlier by the entity.

+ References

No definition available.

+ Details

Name:	nbtb_OriginalAcquisitionPriceOfOwnershipInterest
Namespace Prefix:	nbtb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This line item represents the percentage of ownership interest sold by the wholly owned subsidiary of the entity.

+ References

No definition available.

+ Details

Name:	nbtb_PercentageOfOwnershipInterestSold
Namespace Prefix:	nbtb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow associated with the deconsolidation of a previously consolidated subsidiary or sale of an entity that is related to it but not strictly controlled.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromDivestitureOfInterestInSubsidiariesAndAffiliates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration