Investments - Investments in Unconsolidated Affiliates (Details) - Avion Water - NWN Water - USD ($) $ in Thousands	Jan. 31, 2026	Feb. 28, 2025	Jan. 31, 2024	Jun. 30, 2023	Jul. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Amount	$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000
Ownership percentage of Avion	50.00%	47.90%	45.60%	43.10%	40.30%	37.30%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details