{
 "company": "comcast",
 "ticker": "CMCSA",
 "cusip": "20030N101",
 "security": "Class A common stock",
 "as_of_13f_period": "2026-06-30",
 "generated": "2026-10-31",
 "source": "SEC Form 13F data sets (13F-HR, share positions only; options excluded), https://www.sec.gov/data-research/sec-markets-data/form-13f-data-sets; shares outstanding from 10-Q/10-K cover pages.",
 "excluded_positions": [
  {
   "co": "comcast",
   "period": "2026-06-30",
   "manager": "Sixth Street Partners Management Company, L.P.",
   "shares": 133095082
  },
  {
   "co": "comcast",
   "period": "2024-03-31",
   "manager": "PAYDEN & RYGEL INVESTMENT GROUP",
   "shares": 324330
  },
  {
   "co": "comcast",
   "period": "2023-09-30",
   "manager": "PAYDEN & RYGEL INVESTMENT GROUP",
   "shares": 609730
  }
 ],
 "method": "Institutional % = shares reported on 13F-HR filings for the quarter (latest original or restated filing per manager, plus new-holdings amendments) divided by shares outstanding on the next cover page. 13F totals can double-count where parent and subsidiary managers both report, and exclude non-13F holders. Totals can exceed 100% of shares outstanding, mainly because shares lent to short sellers are reported both by the lending institution and by the buyer.",
 "quarters": [
  {
   "period": "2024-09-30",
   "filers": 2374,
   "inst_shares": 3212767789,
   "shares_out": 3817095628,
   "shares_out_date": "2024-10-15",
   "shares_out_basis": "Class A shares outstanding",
   "inst_pct": 84.2
  },
  {
   "period": "2024-12-31",
   "filers": 2462,
   "inst_shares": 3214629641,
   "shares_out": 3771578226,
   "shares_out_date": "2025-01-15",
   "shares_out_basis": "Class A shares outstanding",
   "inst_pct": 85.2
  },
  {
   "period": "2025-03-31",
   "filers": 2366,
   "inst_shares": 3060847347,
   "shares_out": 3724259552,
   "shares_out_date": "2025-04-15",
   "shares_out_basis": "Class A shares outstanding",
   "inst_pct": 82.2
  },
  {
   "period": "2025-06-30",
   "filers": 2303,
   "inst_shares": 3138464317,
   "shares_out": 3682762127,
   "shares_out_date": "2025-07-15",
   "shares_out_basis": "Class A shares outstanding",
   "inst_pct": 85.2
  },
  {
   "period": "2025-09-30",
   "filers": 2162,
   "inst_shares": 3066217392,
   "shares_out": 3634450130,
   "shares_out_date": "2025-10-15",
   "shares_out_basis": "Class A shares outstanding",
   "inst_pct": 84.4
  },
  {
   "period": "2025-12-31",
   "filers": 2110,
   "inst_shares": 3135682079,
   "shares_out": 3588401619,
   "shares_out_date": "2026-01-15",
   "shares_out_basis": "Class A shares outstanding",
   "inst_pct": 87.4
  },
  {
   "period": "2026-03-31",
   "filers": 2055,
   "inst_shares": 3146180852,
   "shares_out": 3562784182,
   "shares_out_date": "2026-04-15",
   "shares_out_basis": "Class A shares outstanding",
   "inst_pct": 88.3
  },
  {
   "period": "2026-06-30",
   "filers": 1886,
   "inst_shares": 3179159283,
   "shares_out": 3539192198,
   "shares_out_date": "2026-07-15",
   "shares_out_basis": "Class A shares outstanding",
   "inst_pct": 89.8
  }
 ],
 "top_holders": [
  {
   "manager": "Vanguard (all 13F filers)",
   "filer_cik": "fam:VANGUARD",
   "shares": 350923705,
   "pct": 9.92,
   "change_shares": 2967296
  },
  {
   "manager": "BlackRock, Inc.",
   "filer_cik": "0002012383",
   "shares": 313212228,
   "pct": 8.85,
   "change_shares": -1773537
  },
  {
   "manager": "State Street Corp.",
   "filer_cik": "0000093751",
   "shares": 195059449,
   "pct": 5.51,
   "change_shares": 12324336
  },
  {
   "manager": "Charles Schwab Investment Management Inc.",
   "filer_cik": "0000884546",
   "shares": 133095082,
   "pct": 3.76,
   "change_shares": 11536428
  },
  {
   "manager": "Invesco Ltd.",
   "filer_cik": "0000914208",
   "shares": 125126243,
   "pct": 3.54,
   "change_shares": 5324337
  },
  {
   "manager": "Capital Research Global Investors",
   "filer_cik": "0001422848",
   "shares": 116113743,
   "pct": 3.28,
   "change_shares": 26539350
  },
  {
   "manager": "Dodge & Cox",
   "filer_cik": "0000200217",
   "shares": 115903125,
   "pct": 3.27,
   "change_shares": 2794881
  },
  {
   "manager": "Capital World Investors",
   "filer_cik": "0001422849",
   "shares": 104629299,
   "pct": 2.96,
   "change_shares": -77512480
  },
  {
   "manager": "Geode Capital Management, LLC",
   "filer_cik": "0001214717",
   "shares": 89530463,
   "pct": 2.53,
   "change_shares": 1420454
  },
  {
   "manager": "Norges Bank",
   "filer_cik": "0001374170",
   "shares": 76539618,
   "pct": 2.16,
   "change_shares": 76539618
  }
 ],
 "top_holders_trend": {
  "periods": [
   "2024-09-30",
   "2024-12-31",
   "2025-03-31",
   "2025-06-30",
   "2025-09-30",
   "2025-12-31",
   "2026-03-31",
   "2026-06-30"
  ],
  "holders": [
   {
    "manager": "Vanguard (all 13F filers)",
    "filer_cik": "fam:VANGUARD",
    "pct": [
     9.73,
     9.81,
     9.9,
     10.04,
     10.11,
     10.3,
     9.77,
     9.92
    ]
   },
   {
    "manager": "BlackRock, Inc.",
    "filer_cik": "0002012383",
    "pct": [
     7.93,
     7.99,
     8.32,
     8.2,
     8.85,
     8.8,
     8.84,
     8.85
    ]
   },
   {
    "manager": "State Street Corp.",
    "filer_cik": "0000093751",
    "pct": [
     4.3,
     4.45,
     4.53,
     4.69,
     4.97,
     5.21,
     5.13,
     5.51
    ]
   },
   {
    "manager": "Charles Schwab Investment Management Inc.",
    "filer_cik": "0000884546",
    "pct": [
     0.83,
     0.87,
     0.9,
     0.98,
     1.02,
     1.08,
     3.41,
     3.76
    ]
   },
   {
    "manager": "Invesco Ltd.",
    "filer_cik": "0000914208",
    "pct": [
     1.06,
     1.2,
     1.09,
     1.1,
     1.08,
     3.48,
     3.36,
     3.54
    ]
   }
  ]
 },
 "grouping": "Vanguard’s separate 13F filers (The Vanguard Group; from 2026, Vanguard Capital Management and Vanguard Portfolio Management) are combined; other managers are shown per 13F filer.",
 "insiders": {
  "class": "Class A / Class B",
  "rows": [
   {
    "proxy_filed": "2024-04-26",
    "group": "All directors and executive officers (17)",
    "shares": 40268422,
    "pct_reported": "<1% of Class A; 100% of Class B",
    "url": "https://www.sec.gov/Archives/edgar/data/1166691/000130817924000600/cmcsa4226581-def14a.htm",
    "doc": "Proxy statement (DEF 14A)",
    "pct_value": 1.04,
    "pct_basis": "computed: proxy share count ÷ class a shares outstanding as of 2024-07-15"
   },
   {
    "proxy_filed": "2025-04-25",
    "group": "All directors and executive officers (15)",
    "shares": 40081398,
    "pct_reported": "<1% of Class A; 100% of Class B",
    "url": "https://www.sec.gov/Archives/edgar/data/1166691/000130817925000504/cmcsa012438-def14a.htm",
    "doc": "Proxy statement (DEF 14A)",
    "pct_value": 1.08,
    "pct_basis": "computed: proxy share count ÷ class a shares outstanding as of 2025-04-15"
   },
   {
    "proxy_filed": "2026-04-24",
    "group": "All directors and executive officers (14)",
    "shares": 40496859,
    "pct": 1.13,
    "pct_reported": "1.13% of Class A; 100% of Class B",
    "url": "https://www.sec.gov/Archives/edgar/data/1166691/000119312526177138/cmcsa-20260424.htm",
    "doc": "Proxy statement (DEF 14A)",
    "pct_value": 1.13,
    "pct_basis": "reported"
   }
  ],
  "note": "Class B (9,444,375 shares) is held by Brian L. Roberts and carries 33⅓% of the combined voting power."
 }
}