{
  "cik": 1979330,
  "cik_padded": "0001979330",
  "entityName": "NB Bancorp, Inc.",
  "fiscal_years": [
    {
      "accn": "0001104659-26-022367",
      "filed": "2026-03-03",
      "fiscal_year": 2025,
      "form": "10-K",
      "fundamental_units": {
        "buybacks": "USD",
        "capex": "USD",
        "dividends_paid": "USD",
        "eps_diluted": "USD/shares",
        "free_cash_flow": "USD",
        "net_income": "USD",
        "operating_cash_flow": "USD",
        "revenue": "USD",
        "stockholders_equity": "USD",
        "total_assets": "USD",
        "total_liabilities": "USD"
      },
      "fundamentals": {
        "buybacks": 77125000.0,
        "capex": 3417000.0,
        "dividends_paid": 5575000.0,
        "eps_diluted": 1.34,
        "free_cash_flow": 57375000.0,
        "net_income": 50302000.0,
        "operating_cash_flow": 60792000.0,
        "revenue": 335748000.0,
        "stockholders_equity": 858932000.0,
        "total_assets": 7006130000.0,
        "total_liabilities": 6147198000.0
      },
      "period_end": "2025-12-31",
      "ratio_units": {
        "leverage": "ratio",
        "net_margin": "ratio",
        "payout_ratio": "ratio",
        "revenue_growth_yoy": "ratio",
        "roa_avg2y": "ratio",
        "roa_period_end": "ratio",
        "roe_avg2y": "ratio",
        "roe_period_end": "ratio"
      },
      "ratios": {
        "leverage": 7.156792388687347,
        "net_margin": 0.14982069885747645,
        "payout_ratio": 0.11083058327700687,
        "revenue_growth_yoy": 0.14779362496410453,
        "roa_avg2y": 0.008270725090959972,
        "roa_period_end": 0.007179712623088638,
        "roe_avg2y": 0.0619444996887505,
        "roe_period_end": 0.058563425276971864
      }
    },
    {
      "accn": "0001104659-26-022367",
      "filed": "2026-03-03",
      "fiscal_year": 2024,
      "form": "10-K",
      "fundamental_units": {
        "capex": "USD",
        "eps_diluted": "USD/shares",
        "free_cash_flow": "USD",
        "net_income": "USD",
        "operating_cash_flow": "USD",
        "revenue": "USD",
        "stockholders_equity": "USD",
        "total_assets": "USD",
        "total_liabilities": "USD"
      },
      "fundamentals": {
        "capex": 1938000.0,
        "eps_diluted": 1.07,
        "free_cash_flow": 41250000.0,
        "net_income": 42149000.0,
        "operating_cash_flow": 43188000.0,
        "revenue": 292516000.0,
        "stockholders_equity": 765167000.0,
        "total_assets": 5157737000.0,
        "total_liabilities": 4392570000.0
      },
      "period_end": "2024-12-31",
      "ratio_units": {
        "leverage": "ratio",
        "net_margin": "ratio",
        "revenue_growth_yoy": "ratio",
        "roa_avg2y": "ratio",
        "roa_period_end": "ratio",
        "roe_avg2y": "ratio",
        "roe_period_end": "ratio"
      },
      "ratios": {
        "leverage": 5.740668376968688,
        "net_margin": 0.14409126338388328,
        "revenue_growth_yoy": 0.31666104021785607,
        "roa_avg2y": 0.0086984714266492,
        "roa_period_end": 0.008171994810902533,
        "roe_avg2y": 0.05534538836576882,
        "roe_period_end": 0.05508470699860293
      }
    },
    {
      "accn": "0001558370-25-002457",
      "filed": "2026-03-03",
      "fiscal_year": 2023,
      "form": "10-K",
      "fundamental_units": {
        "capex": "USD",
        "eps_diluted": "USD/shares",
        "free_cash_flow": "USD",
        "net_income": "USD",
        "operating_cash_flow": "USD",
        "revenue": "USD",
        "stockholders_equity": "USD",
        "total_assets": "USD",
        "total_liabilities": "USD"
      },
      "fundamentals": {
        "capex": 2865000.0,
        "eps_diluted": 0.23,
        "free_cash_flow": 50034000.0,
        "net_income": 9825000.0,
        "operating_cash_flow": 52899000.0,
        "revenue": 222165000.0,
        "stockholders_equity": 757959000.0,
        "total_assets": 4533391000.0,
        "total_liabilities": 3775432000.0
      },
      "period_end": "2023-12-31",
      "ratio_units": {
        "leverage": "ratio",
        "net_margin": "ratio",
        "revenue_growth_yoy": "ratio",
        "roa_avg2y": "ratio",
        "roa_period_end": "ratio",
        "roe_avg2y": "ratio",
        "roe_period_end": "ratio"
      },
      "ratios": {
        "leverage": 4.9810504262103885,
        "net_margin": 0.044223887651070146,
        "revenue_growth_yoy": 0.8357709469509172,
        "roa_avg2y": 0.0024182454589288392,
        "roa_period_end": 0.002167251843046408,
        "roe_avg2y": 0.017830827640777334,
        "roe_period_end": 0.012962442559557969
      }
    },
    {
      "accn": "0001558370-25-002457",
      "filed": "2026-03-03",
      "fiscal_year": 2022,
      "form": "10-K",
      "fundamental_units": {
        "capex": "USD",
        "free_cash_flow": "USD",
        "net_income": "USD",
        "operating_cash_flow": "USD",
        "revenue": "USD",
        "stockholders_equity": "USD",
        "total_assets": "USD",
        "total_liabilities": "USD"
      },
      "fundamentals": {
        "capex": 8498000.0,
        "free_cash_flow": 31216000.0,
        "net_income": 30065000.0,
        "operating_cash_flow": 39714000.0,
        "revenue": 121020000.0,
        "stockholders_equity": 344065000.0,
        "total_assets": 3592335000.0,
        "total_liabilities": 3248270000.0
      },
      "period_end": "2022-12-31",
      "ratio_units": {
        "leverage": "ratio",
        "net_margin": "ratio",
        "roa_period_end": "ratio",
        "roe_avg2y": "ratio",
        "roe_period_end": "ratio"
      },
      "ratios": {
        "leverage": 9.440861465130135,
        "net_margin": 0.2484300115683358,
        "roa_period_end": 0.008369208328287869,
        "roe_avg2y": 0.08972028994589626,
        "roe_period_end": 0.087381744728467
      }
    },
    {
      "accn": "0001558370-25-002457",
      "filed": "2025-03-07",
      "fiscal_year": 2021,
      "form": "10-K",
      "fundamental_units": {
        "stockholders_equity": "USD"
      },
      "fundamentals": {
        "stockholders_equity": 326129000.0
      },
      "period_end": "2021-12-31",
      "ratios": {}
    }
  ],
  "latest_filing": {
    "accn": "0001104659-26-022367",
    "filed": "2026-03-03",
    "form": "10-K"
  },
  "note": "Static grepcent export of verified SEC companyfacts-derived values. Monetary values are raw reported units from grepcent's resolved facts; no scaling and no FX conversion. Capex, dividends, and buybacks are reported as positive outflow magnitudes. ROE/ROA include both period-end basis (site-consistent) and average-of-two-years basis where the prior-year denominator exists.",
  "schema_version": "1",
  "sic": "6036",
  "sic_description": "Savings Institutions, Not Federally Chartered",
  "source_urls": {
    "sec_companyfacts": "https://data.sec.gov/api/xbrl/companyfacts/CIK0001979330.json",
    "sec_submissions": "https://data.sec.gov/submissions/CIK0001979330.json"
  },
  "ticker": "NBBK"
}