v3.26.1
Average Annual Total Returns
12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
SEQUOIA FUND INC      
Prospectus [Line Items]      
Average Annual Return, Percent 22.13% 10.46% 11.04%
SEQUOIA FUND INC | After Taxes on Distributions      
Prospectus [Line Items]      
Average Annual Return, Percent 19.30% 8.84% 8.36%
SEQUOIA FUND INC | After Taxes on Distributions and Sales      
Prospectus [Line Items]      
Average Annual Return, Percent 14.83% 8.04% 8.10%
​S&P 500 Index (reflects no deduction for fees, expenses or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 17.88% 14.42% 14.82%