Shareholder Report, Line Graph (Details) 190883_Jacob Discovery Fund_Investor Class_TSR Annual {Investor Class} - USD ($) |
12 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Aug. 31, 2025 |
Aug. 31, 2024 |
Aug. 31, 2023 |
Aug. 31, 2022 |
Aug. 31, 2021 |
Aug. 31, 2020 |
Aug. 31, 2019 |
Aug. 31, 2018 |
Aug. 31, 2017 |
Aug. 31, 2016 |
Aug. 31, 2026 |
|
| Investor Class | |||||||||||
| Account Value [Line Items] | |||||||||||
| Accumulated Value | $ 27,486 | $ 21,707 | $ 20,464 | $ 21,786 | $ 40,092 | $ 22,079 | $ 15,789 | $ 15,197 | $ 9,319 | $ 10,000 | $ 30,173 |
| S&P 500 TR [Member] | |||||||||||
| Account Value [Line Items] | |||||||||||
| Line Graph and Table Measure Name | S&P 500 TR | ||||||||||
| Accumulated Value | 34,718 | 29,960 | 23,566 | 20,325 | 22,895 | 17,455 | 14,315 | 13,909 | 11,623 | 10,000 | $ 41,793 |
| Bloomberg US Micro Cap Total Return Index [Member] | |||||||||||
| Account Value [Line Items] | |||||||||||
| Line Graph and Table Measure Name | Bloomberg US Micro Cap Total Return Index | ||||||||||
| Accumulated Value | $ 19,780 | $ 17,214 | $ 15,890 | $ 17,780 | $ 24,281 | $ 13,213 | $ 11,136 | $ 14,405 | $ 11,446 | $ 10,000 | $ 23,842 |