Fair Value of Financial Instruments and Risk Management - Volume of Derivative Activity (Details) GJ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2026 GWh GJ	Dec. 31, 2025 GJ GWh
Electricity swap contracts, Energy contracts subject to regulatory deferral
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (gwh / gj) \| GWh	908	890
Electricity power purchase contracts, Energy contracts subject to regulatory deferral
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (gwh / gj) \| GWh	469	395
Gas swap contracts, Energy contracts subject to regulatory deferral
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (gwh / gj) \| GJ	167	183
Gas supply contract, Energy contracts subject to regulatory deferral
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (gwh / gj) \| GJ	139	147
Wholesale trading contracts, Energy contracts not subject to regulatory deferral
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (gwh / gj) \| GWh	4,291	1,430
Gas swap contracts, Energy Contracts not subject to regulatory deferral
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Volume (gwh / gj) \| GJ	2	2

- Definition

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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