Investment Risks - SEQUOIA FUND INC	Apr. 25, 2025
Risk Lose Money [Member]
Prospectus [Line Items]
Risk [Text Block]	You may lose money by investing in the Fund.
Risk Not Insured [Member]
Prospectus [Line Items]
Risk [Text Block]	An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Nondiversified Status [Member]
Prospectus [Line Items]
Risk [Text Block]	Non-Diversification Risk. The Fund is “non-diversified,” meaning that it invests its assets in a smaller number of companies than many other funds. As a result, your investment in the Fund has the risk that changes in the value of a single security may have a significant effect, either negative or positive, on the Fund’s net asset value per share (“NAV”).
Market Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Market Risk. This is the risk that the market values of the Fund’s investments will decline, perhaps sharply and unpredictably, or fail to rise, for various reasons including changes or potential or perceived changes in U.S. or foreign economies, financial markets, interest rates, the liquidity of investments and other factors including terrorism, war, tariffs, natural disasters and public health events and crises, including disease/virus outbreaks, epidemics and pandemics. The resulting short-term and long-term effects and consequences of such events and factors on global and local economies and specific countries, regions, businesses, industries and companies cannot necessarily be foreseen or predicted. You may lose money by investing in the Fund.
Value Investing Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Value Investing Risk. Investing in undervalued securities involves the risk that such securities may never reach their expected market value, either because the market fails to recognize a security’s intrinsic worth or the expected value was misgauged. Such securities may decline in value even though they are already undervalued.
Foreign (Non-U.S.) Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Foreign (Non-U.S.) Risk. This is the risk that the value of the Fund’s investments in securities of foreign issuers will be affected adversely by foreign economic, social and political conditions and developments or by the application of foreign legal, regulatory, accounting and auditing standards or foreign taxation policies or by currency fluctuations and controls. The risks to the Fund and, therefore, to your investment in the Fund, of investing in foreign securities include expropriation, settlement difficulties, market illiquidity and higher transaction costs. The prices of foreign securities may move in a different direction than the prices of U.S. securities. In addition, the prices of foreign securities may be more volatile than the prices of U.S. securities.
Currency Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Currency Risk. This refers to the risk that securities that trade or are denominated in currencies other than the U.S. Dollar may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. Dollar relative to a foreign currency will generally cause the U.S. Dollar value of an investment denominated in that currency to decline. Currency risk may be hedged or unhedged. Unhedged currency exposure may result in gains or losses as a result of a change in the relationship between the U.S. Dollar and the respective foreign currency.
Growth Company Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Growth Company Risk. The prices of growth securities are often highly sensitive to market fluctuations because of their heavy dependence on future earnings or cash flow expectations, and can be more volatile than the market in general.
Small-Cap and Mid-Cap Company Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Small-Cap and Mid-Cap Company Risk. Investing in securities of small-cap and mid-cap companies may involve greater risks than investing in securities of larger, more established issuers. Small-cap and mid-cap companies may be engaged in business within a narrow geographic region, be less well-known to the investment community and have more volatile share prices. These companies often lack management depth and have narrower market penetrations, less diverse product lines and fewer resources than larger companies. Moreover, the securities of such companies often have less market liquidity and, as a result, their stock prices often react more strongly to changes in the marketplace.
Risks of Investing in a Managed Fund [Member]
Prospectus [Line Items]
Risk [Text Block]	Risks of Investing in a Managed Fund. Performance of individual securities can vary widely. The investment decisions of the Adviser may cause the Fund to underperform other investments or benchmark indices. The Fund may also underperform other mutual funds with similar investment strategies. The Adviser may be incorrect in assessing a particular industry or company, including the anticipated earnings growth of the company. The Adviser may not buy securities at the lowest possible prices or sell securities at the highest possible prices. As with any mutual fund investment, there can be no guarantee that the Fund will achieve its investment goals.
Illiquid Investments Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Illiquid Investments Risk. When there is no willing buyer and a security cannot be readily sold at the desired time or price, the Fund may need to accept a lower price or may not be able to sell the security at all. An inability to sell securities, at the Fund’s desired price or at all, can adversely affect the Fund’s value or prevent the Fund from being able to take advantage of other investment opportunities.
Capital Gain Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Capital Gain Risk. As of the date of this Prospectus, a substantial portion of the Fund’s NAV is attributable to realized and/or net unrealized capital gains on portfolio securities. If the Fund realizes capital gains in excess of realized capital losses in any fiscal year, it generally expects to make capital gain distributions to shareholders. You may receive distributions that are attributable to appreciation of portfolio securities that happened before you made your investment. Unless you purchase shares through a tax-advantaged account (such as an IRA or 401(k) plan), these distributions will be taxable to you even though they economically represent a return of a portion of your investment. If such distribution is reinvested in Fund shares, any such income or gain will increase the tax basis of your shares, which will reduce the amount of gain or increase the amount of loss you recognize on a disposition of your shares. You should consult your tax professional about your investment in the Fund.

Investment Risks - SEQUOIA FUND INC

Apr. 25, 2025

You may lose money by investing in the Fund.

An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Risk Nondiversified Status [Member]

Prospectus [Line Items]

Risk [Text Block]

Non-Diversification Risk. The Fund is “non-diversified,” meaning that it invests its assets in a smaller number of companies than many other funds. As a result, your investment in the Fund has the risk that changes in the value of a single security may have a significant effect, either negative or positive, on the Fund’s net asset value per share (“NAV”).

Market Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Market Risk. This is the risk that the market values of the Fund’s investments will decline, perhaps sharply and unpredictably, or fail to rise, for various reasons including changes or potential or perceived changes in U.S. or foreign economies, financial markets, interest rates, the liquidity of investments and other factors including terrorism, war, tariffs, natural disasters and public health events and crises, including disease/virus outbreaks, epidemics and pandemics. The resulting short-term and long-term effects and consequences of such events and factors on global and local economies and specific countries, regions, businesses, industries and companies cannot necessarily be foreseen or predicted. You may lose money by investing in the Fund.

Value Investing Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Value Investing Risk. Investing in undervalued securities involves the risk that such securities may never reach their expected market value, either because the market fails to recognize a security’s intrinsic worth or the expected value was misgauged. Such securities may decline in value even though they are already undervalued.

Foreign (Non-U.S.) Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Foreign (Non-U.S.) Risk. This is the risk that the value of the Fund’s investments in securities of foreign issuers will be affected adversely by foreign economic, social and political conditions and developments or by the application of foreign legal, regulatory, accounting and auditing standards or foreign taxation policies or by currency fluctuations and controls. The risks to the Fund and, therefore, to your investment in the Fund, of investing in foreign securities include expropriation, settlement difficulties, market illiquidity and higher transaction costs. The prices of foreign securities may move in a different direction than the prices of U.S. securities. In addition, the prices of foreign securities may be more volatile than the prices of U.S. securities.

Currency Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Currency Risk. This refers to the risk that securities that trade or are denominated in currencies other than the U.S. Dollar may be affected by fluctuations in currency exchange rates. An increase in the strength of the U.S. Dollar relative to a foreign currency will generally cause the U.S. Dollar value of an investment denominated in that currency to decline. Currency risk may be hedged or unhedged. Unhedged currency exposure may result in gains or losses as a result of a change in the relationship between the U.S. Dollar and the respective foreign currency.

Growth Company Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Growth Company Risk. The prices of growth securities are often highly sensitive to market fluctuations because of their heavy dependence on future earnings or cash flow expectations, and can be more volatile than the market in general.

Small-Cap and Mid-Cap Company Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Small-Cap and Mid-Cap Company Risk. Investing in securities of small-cap and mid-cap companies may involve greater risks than investing in securities of larger, more established issuers. Small-cap and mid-cap companies may be engaged in business within a narrow geographic region, be less well-known to the investment community and have more volatile share prices. These companies often lack management depth and have narrower market penetrations, less diverse product lines and fewer resources than larger companies. Moreover, the securities of such companies often have less market liquidity and, as a result, their stock prices often react more strongly to changes in the marketplace.

Risks of Investing in a Managed Fund [Member]

Prospectus [Line Items]

Risk [Text Block]

Risks of Investing in a Managed Fund. Performance of individual securities can vary widely. The investment decisions of the Adviser may cause the Fund to underperform other investments or benchmark indices. The Fund may also underperform other mutual funds with similar investment strategies. The Adviser may be incorrect in assessing a particular industry or company, including the anticipated earnings growth of the company. The Adviser may not buy securities at the lowest possible prices or sell securities at the highest possible prices. As with any mutual fund investment, there can be no guarantee that the Fund will achieve its investment goals.

Illiquid Investments Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Illiquid Investments Risk. When there is no willing buyer and a security cannot be readily sold at the desired time or price, the Fund may need to accept a lower price or may not be able to sell the security at all. An inability to sell securities, at the Fund’s desired price or at all, can adversely affect the Fund’s value or prevent the Fund from being able to take advantage of other investment opportunities.

Capital Gain Risk [Member]

Prospectus [Line Items]

Risk [Text Block]

Capital Gain Risk. As of the date of this Prospectus, a substantial portion of the Fund’s NAV is attributable to realized and/or net unrealized capital gains on portfolio securities. If the Fund realizes capital gains in excess of realized capital losses in any fiscal year, it generally expects to make capital gain distributions to shareholders. You may receive distributions that are attributable to appreciation of portfolio securities that happened before you made your investment. Unless you purchase shares through a tax-advantaged account (such as an IRA or 401(k) plan), these distributions will be taxable to you even though they economically represent a return of a portion of your investment. If such distribution is reinvested in Fund shares, any such income or gain will increase the tax basis of your shares, which will reduce the amount of gain or increase the amount of loss you recognize on a disposition of your shares. You should consult your tax professional about your investment in the Fund.