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S000003464 [Member] Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Russell 3000® Index (reflects no deduction for fees, expenses or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 17.15% 13.15% 14.29%
Russell 2000® Growth Index (reflects no deduction for fees, expenses or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent [2] 13.01% 3.18% 9.57%
Sit Small Cap Growth Fund      
Prospectus [Line Items]      
Average Annual Return, Percent 9.43% 4.66% 8.96%
Sit Small Cap Growth Fund | After Taxes on Distributions      
Prospectus [Line Items]      
Average Annual Return, Percent 8.09% 3.22% 7.65%
Sit Small Cap Growth Fund | After Taxes on Distributions and Sales      
Prospectus [Line Items]      
Average Annual Return, Percent 6.55% 3.50% 7.07%
[1]
A broad-based securities market index that represents the overall domestic equity markets.
[2]
A more narrowly-based index that reflects the market sectors in which the Fund invests.