Shareholder Report, Average Annual Return (Details) |
6 Months Ended | 12 Months Ended | 60 Months Ended | 120 Months Ended |
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2026 |
Jun. 30, 2026 |
Jun. 30, 2026 |
|
| C000013290 | ||||
| Average Annual Return [Line Items] | ||||
| Line Graph and Table Measure Name | New Alternatives Fund | |||
| Average Annual Return, Percent | 13.99% | 22.37% | 2.12% | 9.99% |
| C000146229 | ||||
| Average Annual Return [Line Items] | ||||
| Line Graph and Table Measure Name | New Alternatives Fund | |||
| Without Sales Load [Member] | C000013290 | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 18.13% | 26.81% | 2.85% | 10.52% |
| Without Sales Load [Member] | C000146229 | ||||
| Average Annual Return [Line Items] | ||||
| Average Annual Return, Percent | 17.98% | 26.50% | 2.59% | 10.25% |
| S&P 500 Index TR | ||||
| Average Annual Return [Line Items] | ||||
| Line Graph and Table Measure Name | S&P 500<sup style="inset: 1.5px 0px 4px; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 700; grid-area: auto; line-height: 0px; margin: 0px; overflow: visible; position: relative; text-align: center; text-align-last: auto; white-space-collapse: preserve-breaks;">®</sup> Index | |||
| Average Annual Return, Percent | 10.21% | 22.32% | 13.41% | 15.51% |
| S&P 500 Index TR | ||||
| Average Annual Return [Line Items] | ||||
| Line Graph and Table Measure Name | S&P 500<sup style="inset: 1.5px 0px 4px; box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 700; grid-area: auto; line-height: 0px; margin: 0px; overflow: visible; position: relative; text-align: center; text-align-last: auto; white-space-collapse: preserve-breaks;">®</sup> Index | |||
| Average Annual Return, Percent | 10.21% | 22.32% | 13.41% | 15.51% |