Shareholder Report, Line Graph (Details) 190883_Jacob Discovery Fund_Institutional Class_TSR Annual {Institutional 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 |
|
| Institutional Class | |||||||||||
| Account Value [Line Items] | |||||||||||
| Accumulated Value | $ 281,420 | $ 221,632 | $ 208,266 | $ 221,090 | $ 405,764 | $ 222,874 | $ 159,042 | $ 152,766 | $ 93,476 | $ 100,000 | $ 309,861 |
| S&P 500 TR [Member] | |||||||||||
| Account Value [Line Items] | |||||||||||
| Line Graph and Table Measure Name | S&P 500 TR | ||||||||||
| Accumulated Value | 347,177 | 299,601 | 235,655 | 203,248 | 228,955 | 174,554 | 143,151 | 139,088 | 116,234 | 100,000 | $ 417,931 |
| 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 | $ 197,797 | $ 172,143 | $ 158,896 | $ 177,799 | $ 242,812 | $ 132,131 | $ 111,358 | $ 144,046 | $ 114,465 | $ 100,000 | $ 238,421 |