Shareholder Report, Holdings (Details)	Jun. 30, 2026
C000013290 \| B288C92 \| Iberdrola S.A.
Holdings [Line Items]
Percent of Net Asset Value	5.60%
C000013290 \| 5579107 \| Acciona S.A.
Holdings [Line Items]
Percent of Net Asset Value	5.50%
C000013290 \| 4031879 \| Veolia Environnement S.A.
Holdings [Line Items]
Percent of Net Asset Value	5.30%
C000013290 \| 7144569 \| Enel SpA
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000013290 \| 5727973 \| Siemens A.G.
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000013290 \| 6459286 \| Infratil Ltd.
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000013290 \| 41068X100 \| HA Sustainable Infrastructure Capital, Inc.
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000013290 \| B01BN57 \| Terna - Rete Elettrica Nazionale
Holdings [Line Items]
Percent of Net Asset Value	4.80%
C000013290 \| 11285B108 \| Brookfield Renewable Corporation
Holdings [Line Items]
Percent of Net Asset Value	4.70%
C000013290 \| 18539C204 \| Clearway Energy, Inc., Class C
Holdings [Line Items]
Percent of Net Asset Value	4.40%
C000146229 \| B288C92 \| Iberdrola S.A.
Holdings [Line Items]
Percent of Net Asset Value	5.60%
C000146229 \| 5579107 \| Acciona S.A.
Holdings [Line Items]
Percent of Net Asset Value	5.50%
C000146229 \| 4031879 \| Veolia Environnement S.A.
Holdings [Line Items]
Percent of Net Asset Value	5.30%
C000146229 \| 7144569 \| Enel SpA
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000146229 \| 5727973 \| Siemens A.G.
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000146229 \| 6459286 \| Infratil Ltd.
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000146229 \| 41068X100 \| HA Sustainable Infrastructure Capital, Inc.
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000146229 \| B01BN57 \| Terna - Rete Elettrica Nazionale
Holdings [Line Items]
Percent of Net Asset Value	4.80%
C000146229 \| 11285B108 \| Brookfield Renewable Corporation
Holdings [Line Items]
Percent of Net Asset Value	4.70%
C000146229 \| 18539C204 \| Clearway Energy, Inc., Class C
Holdings [Line Items]
Percent of Net Asset Value	4.40%