Annual Fund Operating Expenses |
Mar. 31, 2026 |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Needham Growth Fund | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Fee Waiver or Reimbursement over Assets, Date of Termination | March 31, 2027 | |||||||||||
| Needham Growth Fund | Needham Growth Fund, Retail Class | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Management Fees (as a percentage of Assets) | 1.25% | |||||||||||
| Distribution and Service (12b-1) Fees | 0.25% | |||||||||||
| Component1 Other Expenses | 0.24% | |||||||||||
| Expenses (as a percentage of Assets) | 1.74% | |||||||||||
| Fee Waiver or Reimbursement | (0.07%) | [1] | ||||||||||
| Net Expenses (as a percentage of Assets) | 1.67% | |||||||||||
| Needham Growth Fund | Needham Growth Fund, Institutional Class | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Management Fees (as a percentage of Assets) | 1.25% | |||||||||||
| Distribution and Service (12b-1) Fees | 0.00% | |||||||||||
| Component1 Other Expenses | 0.22% | |||||||||||
| Expenses (as a percentage of Assets) | 1.47% | |||||||||||
| Fee Waiver or Reimbursement | (0.29%) | [1] | ||||||||||
| Net Expenses (as a percentage of Assets) | 1.18% | |||||||||||
| Needham Aggressive Growth Fund | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Fee Waiver or Reimbursement over Assets, Date of Termination | March 31, 2027 | |||||||||||
| Needham Aggressive Growth Fund | Needham Aggressive Growth Fund, Retail Class | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Management Fees (as a percentage of Assets) | 1.25% | |||||||||||
| Distribution and Service (12b-1) Fees | 0.25% | |||||||||||
| Component1 Other Expenses | 0.20% | |||||||||||
| Other Expenses (as a percentage of Assets): | 1.70% | |||||||||||
| Acquired Fund Fees and Expenses | 0.01% | [2] | ||||||||||
| Expenses (as a percentage of Assets) | 1.71% | |||||||||||
| Fee Waiver or Reimbursement | (0.07%) | [3] | ||||||||||
| Net Expenses (as a percentage of Assets) | 1.64% | |||||||||||
| Needham Aggressive Growth Fund | Needham Aggressive Growth Fund, Institutional Class | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Management Fees (as a percentage of Assets) | 1.25% | |||||||||||
| Distribution and Service (12b-1) Fees | 0.00% | |||||||||||
| Component1 Other Expenses | 0.20% | |||||||||||
| Other Expenses (as a percentage of Assets): | 1.45% | |||||||||||
| Acquired Fund Fees and Expenses | 0.01% | [2] | ||||||||||
| Expenses (as a percentage of Assets) | 1.46% | |||||||||||
| Fee Waiver or Reimbursement | (0.27%) | [3] | ||||||||||
| Net Expenses (as a percentage of Assets) | 1.19% | |||||||||||
| Needham Small Cap Growth Fund | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Fee Waiver or Reimbursement over Assets, Date of Termination | March 31, 2027 | |||||||||||
| Needham Small Cap Growth Fund | Needham Small Cap Growth Fund, Retail Class | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Management Fees (as a percentage of Assets) | 1.25% | |||||||||||
| Distribution and Service (12b-1) Fees | 0.25% | |||||||||||
| Component2 Other Expenses | 0.10% | [4] | ||||||||||
| Component3 Other Expenses | 0.25% | |||||||||||
| Other Expenses (as a percentage of Assets): | 1.85% | |||||||||||
| Acquired Fund Fees and Expenses | 0.01% | [5] | ||||||||||
| Expenses (as a percentage of Assets) | 1.86% | |||||||||||
| Fee Waiver or Reimbursement | (0.07%) | [4] | ||||||||||
| Net Expenses (as a percentage of Assets) | 1.79% | |||||||||||
| Needham Small Cap Growth Fund | Needham Small Cap Growth Fund, Institutional Class | ||||||||||||
| Prospectus [Line Items] | ||||||||||||
| Management Fees (as a percentage of Assets) | 1.25% | |||||||||||
| Distribution and Service (12b-1) Fees | 0.00% | |||||||||||
| Component2 Other Expenses | 0.00% | [4] | ||||||||||
| Component3 Other Expenses | 0.21% | |||||||||||
| Other Expenses (as a percentage of Assets): | 1.46% | |||||||||||
| Acquired Fund Fees and Expenses | 0.01% | [5] | ||||||||||
| Expenses (as a percentage of Assets) | 1.47% | |||||||||||
| Fee Waiver or Reimbursement | (0.28%) | [4] | ||||||||||
| Net Expenses (as a percentage of Assets) | 1.19% | |||||||||||
| ||||||||||||