No definition available.

Name:	fhlbbost_AHPVoluntaryContributionExpense
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Affordable Housing Program distributions in the form of an Advance that is below market value interest rates.

No definition available.

Name:	fhlbbost_AffordableHousingProgramAdvanceSubsidies
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Maximum contribution amount to the Affordable Housing Program (AHP) calculated based on net income before interest expense associated with mandatorily redeemable capital stock and the assessment for AHP, but after any assessment for the Resolution Fiunding Corporation

No definition available.

Name:	fhlbbost_AffordableHousingProgramContributionRequirementAmount
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Maximum contribution percentage to the Affordable Housing Program (AHP) calculated based on net income before interest expense associated with mandatorily redeemable capital stock and the assessment for AHP, but after any assessment for the Resolution Fiunding Corporation

No definition available.

Name:	fhlbbost_AffordableHousingProgramContributionRequirementPercent
Namespace Prefix:	fhlbbost_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Affordable Housing Program [Line Items]

No definition available.

Name:	fhlbbost_AffordableHousingProgramLineItems
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Affordable Housing Programs Return of Previously Disbursed Grants and Subsidies

No definition available.

Name:	fhlbbost_AffordableHousingProgramsReturnOfPreviouslyDisbursedGrantsAndSubsidies
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

Name:	fhlbbost_DiscretionaryHousingAndCommunityInvestmentsRollForward
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Subsidy expense for discretionary housing and community investment programs

No definition available.

Name:	fhlbbost_SubsidyExpenseForDiscretionaryHousingAndCommunityInvestmentPrograms
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of liability related to Voluntary contributions (non-AHP).

No definition available.

Name:	fhlbbost_VoluntaryContributionLiabilityBalance
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Voluntary contribution amounts recaptured that were previously distributed and other amounts, net.

No definition available.

Name:	fhlbbost_VoluntaryContributionReturnOfPreviouslyDisbursedSubsidies
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of cash outflow for payments made by the Federal Home Loan Banks (FHLBanks) to Voluntary contributions (non-AHP).

No definition available.

Name:	fhlbbost_VoluntaryGrantDisbursements
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Voluntary distributions in the form of Advances or other loans that are below market value interest rates.

No definition available.

Name:	fhlbbost_VoluntarySubsidyForAdvanceDisbursements
Namespace Prefix:	fhlbbost_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of expense for Affordable Housing Program (AHP) assessments required by the Federal Home Loan Bank Act of 1932.

No definition available.

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

Amount of obligation related to Affordable Housing Program (AHP) assessments required by the Federal Home Loan Bank Act of 1932.

No definition available.

Name:	us-gaap_AffordableHousingProgramObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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

Amount of cash outflow for payments made by the Federal Home Loan Banks (FHLBanks) to the Affordable Housing Program (AHP).

No definition available.

Federal Home Loan Bank of Boston 10-K