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Total anticipated costs associated with remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal, or abandonment of a particular property resulting from unanticipated contamination of the assets.

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Environmental Matters - Narrative (Details) $ in Millions	1 Months Ended	6 Months Ended
Environmental Matters - Narrative (Details) $ in Millions	Jan. 31, 2017	Jun. 30, 2026 USD ($) complaint party property mi	Oct. 09, 2024
Site Contingency [Line Items]
Annual tariff rider collection		$ 5.0
Annual insurance proceeds to apply against remediation costs		5.0
Total annual remediation expense and interest		$ 10.0
Enrolled customers during time period (in years)			6 years
Portland Harbor
Site Contingency [Line Items]
Number of miles \| mi		10
Number of potentially responsible parties (more than) \| party		100
EPA final feasibility study and proposed remediation plan, clean-up costs, portland harbor		$ 1,050.0
Number of remediation projects \| property		2
Portland Harbor \| Minimum
Site Contingency [Line Items]
Percentage of clean-up costs	(30.00%)
Portland Harbor \| Maximum
Site Contingency [Line Items]
Percentage of clean-up costs	50.00%
Gasco Sediments
Site Contingency [Line Items]
Site contingency, environmental remediation costs recognized		$ 53.0
Gasco Sediments \| Minimum
Site Contingency [Line Items]
Environmental exit costs, anticipated cost		53.0
Gasco Sediments \| Maximum
Site Contingency [Line Items]
Environmental exit costs, anticipated cost		$ 350.0
Other Portland Harbor \| Yakama Nation
Site Contingency [Line Items]
Trustee council members - number of claimants		1
Site contingency, number of other third-party defendants		29
NRD liability claim yakama nation		$ 0.3
Number of amended complaints filed \| complaint		2
Gasco Uplands
Site Contingency [Line Items]
Site contingency number of management pieces		2
Gasco Uplands \| Minimum
Site Contingency [Line Items]
Environmental exit costs, anticipated cost		$ 284.0
Gasco Uplands \| Maximum
Site Contingency [Line Items]
Environmental exit costs, anticipated cost		$ 950.0
Gasco Upland Site
Site Contingency [Line Items]
Undiscounted monitoring costs (in years)		30 years
Gasco Upland Site \| Minimum
Site Contingency [Line Items]
Environmental exit costs, anticipated cost		$ 230.0
Gasco Upland Site \| Maximum
Site Contingency [Line Items]
Environmental exit costs, anticipated cost		250.0
Gasco Uplands IRAM \| Minimum
Site Contingency [Line Items]
Environmental exit costs, anticipated cost		9.0
Gasco Uplands IRAM \| Maximum
Site Contingency [Line Items]
Environmental exit costs, anticipated cost		78.0
Front Street site
Site Contingency [Line Items]
Additional studies and design costs		$ 0.8
Oregon
Site Contingency [Line Items]
Remediation recovery percentage		96.70%
WASHINGTON
Site Contingency [Line Items]
Remediation recovery percentage		3.30%