SEQUOIA FUND INC SEQUOIA FUND INC Market Risk [Member] Value Investing Risk [Member] Foreign (Non-U.S.) Risk [Member] Currency Risk [Member] Growth Company Risk [Member] Small-Cap and Mid-Cap Company Risk [Member] Risks of Investing in a Managed Fund [Member] Illiquid Investments Risk [Member] Capital Gain Risk [Member] ​S&P 500 Index (reflects no deduction for fees, expenses or taxes) Value Investing Risk Member Market Risk Member Foreign Non USRisk Member Currency Risk Member Growth Company Risk Member Illiquid Investments Risk Member C000033159 Member Small Cap And Mid Cap Company Risk Member Risks Of Investing In AManaged Fund Member index_ SP_500_ Index_reflects_no_deduction_for_fees_expenses_or_taxes Member S000012155 Member Capital Gain Risk Member