Shareholder Report, Average Annual Return (Details) 190883_Jacob Discovery Fund_Investor Class_TSR Annual {Investor Class} |
12 Months Ended | 60 Months Ended | 120 Months Ended |
|---|---|---|---|
Aug. 31, 2026 |
Aug. 31, 2026 |
Aug. 31, 2026 |
|
| Without Sales Load [Member] | Investor Class | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Investor Class (without sales charge) | ||
| Average Annual Return, Percent | 9.78% | (5.53%) | 11.68% |
| S&P 500 TR [Member] | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | S&P 500 TR | ||
| Average Annual Return, Percent | 20.38% | 12.79% | 15.37% |
| Bloomberg US Micro Cap Total Return Index [Member] | |||
| Average Annual Return [Line Items] | |||
| Line Graph and Table Measure Name | Bloomberg US Micro Cap Total Return Index | ||
| Average Annual Return, Percent | 20.54% | (0.36%) | 9.08% |