BORROWED FUNDS - Additional Information (Details) - USD ($)	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Outstanding amount	$ 373,672,000	$ 183,198,000
Financial Guarantee \| NHTB Capital Trust II and NHTB Capital Trust III
Debt Instrument [Line Items]
Debentures issued by variable interest entities	$ 20,600,000
LIBOR \| Financial Guarantee
Debt Instrument [Line Items]
Interest rate margin	2.79%
Advances from the FHLB
Debt Instrument [Line Items]
Line of credit maintained	$ 1,000,000.0
Outstanding balance on the FHLB line of credit	0	0
Outstanding amount	182,609,000	123,278,000
Federal Home Loan Bank Certificates and Obligations FHLB Callable Advances
Debt Instrument [Line Items]
Outstanding amount	2,000,000.0	0
Federal Home Loan Bank Certificates and Obligations FHLB Amortizing Advances
Debt Instrument [Line Items]
Outstanding amount	309,000	316,000
Federal Reserve Bank Advances
Debt Instrument [Line Items]
Line of credit maintained	81,100,000
Outstanding amount	131,143,000
Federal Reserve Bank Advances \| Unsecured Debt
Debt Instrument [Line Items]
Line of credit maintained	50,000,000.0	50,000,000.0
Outstanding balance on unused unsecured federal funds line of credit	$ 0	$ 0

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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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.

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- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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-Publisher FASB
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- Definition

Fair value of the amount outstanding under the credit facility.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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