Schedule H, Line 4i - Schedule of Assets (Held at End of Year) (Details) - Needham Bank 401(k) Plan
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12 Months Ended |
|
Dec. 31, 2025
USD ($)
|
|---|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Plan Name |
NEEDHAM BANK 401(k) PLAN
|
| Entity tax identification number |
84-3556185
|
| Plan number |
003
|
| Notes receivable from participants |
$ 914,865
|
| Total Investments and Loans |
$ 68,774,693
|
| Investment assets acquired |
0
|
| Investment assets disposed |
0
|
| Minimum |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Interest rates of notes receivable from participants |
2.80%
|
| Maximum |
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| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Interest rates of notes receivable from participants |
10.50%
|
| Investment, Identifier [Axis]: AB, Bond Inflation Strategy Portfolio, Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:AbMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 167,890
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Capital Research and Management Co, New World Fund Inc. , Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:CapitalResearchAndManagementCoMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 362,034
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Dimensional Fund Advisors, US Small Cap Portfolio, Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:DimensionalFundAdvisorsMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 1,337,275
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Fidelity Investments, Fidelity 500 Index Fund, Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:FidelityInvestmentsMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 6,848,493
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Massachusetts Financial Service Co Institutional Trust, MFS International Equity Fund, Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:MassachusettsFinancialServiceCoInstitutionalTrustMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 1,285,907
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: NB Bancorp, Inc. Common Stock |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:NbBancorpIncMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Common stock
|
| Current Value |
$ 11,892,043
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: PGIM, High Yield Fund, Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:PgimMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 78,202
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: PIMCO, Income Fund, Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:PimcoMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 1,205,840
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Funds Inc, Principal Government Money Market Fund, Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalFundsIncMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 821,432
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Blue Chip SA-Z, Pooled Separate Accounts |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Pooled separate accounts
|
| Current Value |
$ 4,208,159
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Equity Income SA-Z, Pooled Separate Accounts |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Pooled separate accounts
|
| Current Value |
$ 1,848,185
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Fixed Income SA-Z, Pooled Separate Accounts |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Pooled separate accounts
|
| Current Value |
$ 252,537
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2015 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 91,107
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2020 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 1,771,796
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2025 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 4,618,879
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2030 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 3,116,538
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2035 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 3,076,313
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2040 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 5,933,740
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2045 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 2,906,482
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2050 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 5,628,352
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2055 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 2,814,529
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2060 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 2,280,662
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2065 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 701,505
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime 2070 CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 343,182
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, Lifetime Strategic Income CIT Tier I, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Collective investment trusts
|
| Current Value |
$ 592,739
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, MidCap Growth SA-Z, Pooled Separate Accounts |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Pooled separate accounts
|
| Current Value |
$ 671,324
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, MidCap S And P 400 Index SA-Z, Pooled Separate Accounts |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Pooled separate accounts
|
| Current Value |
$ 190,392
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, MidCap Value I SA-Z, Pooled Separate Accounts |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Pooled separate accounts
|
| Current Value |
$ 102,651
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Global Investors Trust Company, SmallCap Value II SA-Z, Pooled Separate Accounts |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalGlobalInvestorsTrustCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Pooled separate accounts
|
| Current Value |
$ 27,442
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Principal Life Insurance Company, Principal Fixed Guaranteed Option, Collective Investment Trust |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| EBP, Asset Held for Investment, Party-in-Interest [true false] |
true
|
| Investment issuer name |
nbbk:PrincipalLifeInsuranceCompanyMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Traditional investment contract
|
| Current Value |
$ 1,997,652
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Self-Directed Brokerage Accounts |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:SelfDirectedBrokerageAccountsMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Self-directed brokerage accounts
|
| Current Value |
$ 567,911
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|
| Investment, Identifier [Axis]: Vanguard Group, Vanguard Explorer Fund, Mutual Funds |
|
| Schedule H, Line 4i - Schedule of Assets (Held at End of Year) |
|
| Investment issuer name |
nbbk:VanguardGroupMember
|
| EBP, Investment, Current Value, Type [Extensible Enumeration] |
Mutual funds
|
| Current Value |
$ 118,635
|
| EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] |
us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
|