Average Annual Total Returns |
12 Months Ended | 60 Months Ended | 120 Months Ended | |
|---|---|---|---|---|
Apr. 30, 2026 |
Dec. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2025 |
|
| NEW ALTERNATIVES FUND Investor Shares | ||||
| Prospectus [Line Items] | ||||
| Average Annual Return, Label [Optional Text] | Return Before Taxes | |||
| Average Annual Return, Percent | 27.82% | (1.48%) | 9.34% | |
| NEW ALTERNATIVES FUND CLASS A SHARES | ||||
| Prospectus [Line Items] | ||||
| Average Annual Return, Label [Optional Text] | Return Before Taxes | |||
| Average Annual Return, Percent | 23.66% | (1.93%) | 9.08% | |
| NEW ALTERNATIVES FUND CLASS A SHARES | After Taxes on Distributions | ||||
| Prospectus [Line Items] | ||||
| Average Annual Return, Percent | 27.76% | (2.24%) | 8.16% | |
| NEW ALTERNATIVES FUND CLASS A SHARES | After Taxes on Distributions and Sales | ||||
| Prospectus [Line Items] | ||||
| Average Annual Return, Percent | 16.89% | (1.10%) | 7.29% | |
| NEW ALTERNATIVES FUND CLASS A SHARES | S&P 500® Index (reflects no deduction of fees, expenses and taxes) | ||||
| Prospectus [Line Items] | ||||
| Average Annual Return, Percent | 17.88% | 14.42% | 14.82% |