| Form N-CSR Cover | 6 Months Ended |
| Jun. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | SEQUOIA FUND INC |
| Entity Central Index Key | 0000089043 |
| Document Period End Date | Jun. 30, 2024 |
| Shareholder Report | 6 Months Ended | |
| Jun. 30, 2024 USD ($) Holding | ||
| Shareholder Report [Line Items] | ||
| Document Type | N-CSRS | |
| Amendment Flag | false | |
| Registrant Name | SEQUOIA FUND INC | |
| Entity Central Index Key | 0000089043 | |
| Document Period End Date | Jun. 30, 2024 | |
| C000033159 [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Sequoia Fund, Inc. | |
| Class Name | Sequoia Fund, Inc. | |
| Trading Symbol | SEQUX | |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Sequoia Fund, Inc. (the “Fund”) for the period of January 1, 2024 to June 30, 2024. | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.sequoiafund.com/resources. You can also request this information by contacting us at 1-800-686-6884. | |
| Additional Information Phone Number | 1-800-686-6884 | |
| Additional Information Website | www.sequoiafund.com/resources | |
| Expenses [Text Block] | Fund Expenses (Based on a hypothetical $10,000 investment) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Sequoia Fund, Inc. $ 1.00 % * * Annualized | |
| Expenses Paid, Amount | $ 53 | |
| Expense Ratio, Percent | 1% | [1] |
| Net Assets | $ 3,450,694,267 | |
| Holdings Count | Holding | 22 | |
| Investment Company Portfolio Turnover | 1% | |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Net assets $ % Total number of portfolio holdings $ % Portfolio turnover rate as of the end of the reporting period $ % | |
| Holdings [Text Block] | Fund Holdings (as of June 30, 2024) The following table and graph show the investment makeup of the Fund as of June 30, 2024. Figures are expressed as percentages of the Fund’s net assets. Top Ten Holdings Rolls-Royce Holdings PLC 8.3 % Alphabet, Inc. 7.3 % Intercontinental Exchange, Inc. 7.0 % Constellation Software, Inc. 6.9 % The Charles Schwab Corp. 6.4 % Liberty Media Corp.-Liberty Formula One 5.8 % Taiwan Semiconductor Manufacturing Co., Ltd. 5.6 % UnitedHealth Group, Inc. 5.5 % Universal Music Group NV 5.3 % Elevance Health, Inc. 5.2 % Sector Allocation | |
| Largest Holdings [Text Block] | Top Ten Holdings Rolls-Royce Holdings PLC 8.3 % Alphabet, Inc. 7.3 % Intercontinental Exchange, Inc. 7.0 % Constellation Software, Inc. 6.9 % The Charles Schwab Corp. 6.4 % Liberty Media Corp.-Liberty Formula One 5.8 % Taiwan Semiconductor Manufacturing Co., Ltd. 5.6 % UnitedHealth Group, Inc. 5.5 % Universal Music Group NV 5.3 % Elevance Health, Inc. 5.2 % | |
| [1]Annualized | ||
| Shareholder Report, Holdings (Details) - C000033159 [Member] | Jun. 30, 2024 |
| Rolls Royce Holdings PLC [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.30% |
| Alphabet Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.30% |
| Intercontinental Exchange Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7% |
| Constellation Software Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.90% |
| The Charles Schwab Corp [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.40% |
| Liberty Media Corp Liberty Formula One [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.80% |
| Taiwan Semiconductor Manufacturing Co Ltd [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| UnitedHealth Group Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.50% |
| Universal Music Group NV [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.30% |
| Elevance Health Inc [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| Application Software [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.40% |
| Movies And Entertainment [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.10% |
| Managed Health Care [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| Interactive Media And Services [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.60% |
| Consumer Finance [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.50% |
| Aerospace And Defense [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.20% |
| Financial Exchanges And Data [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7% |
| Investment Banking And Brokerage [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.40% |
| Semiconductors [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| Research And Consulting Services [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| Life Sciences Tools And Services [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| Cable And Satellite [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Automotive Retail [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.10% |
| Trading Companies And Distributors [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Multi Sector Holdings [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
