Annual Total Returns |
12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Needham Growth Fund | Needham Growth Fund, Retail Class | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 9.06% | 14.51% | 26.85% | (33.66%) | 27.68% | 41.59% | 42.31% | (10.26%) | 8.32% | 10.57% |
| Needham Aggressive Growth Fund | Needham Aggressive Growth Fund, Retail Class | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 26.51% | 14.31% | 37.65% | (27.53%) | 37.54% | 51.39% | 43.93% | (15.80%) | 8.73% | 22.18% |
| Needham Small Cap Growth Fund | Needham Small Cap Growth Fund, Retail Class | ||||||||||
| Prospectus [Line Items] | ||||||||||
| Annual Return [Percent] | 10.50% | 12.76% | 5.68% | (30.33%) | 10.98% | 71.35% | 54.45% | (5.13%) | 11.88% | 31.26% |