Recurring Fair Value Measurements (Details) - USD ($)		12 Months Ended
		Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Return Cash Collateral		$ 0	$ 0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value Hedges, Net		0	0	$ 0
Commodity Contract [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning of period		67,000,000	39,000,000	119,000,000
Purchases	[1]	201,000,000	138,000,000	79,000,000
Settlements	[1]	(202,000,000)	(242,000,000)	(89,000,000)
Gains (losses) recognized as regulatory assets	[1]	13,000,000	132,000,000	(70,000,000)
Balance at end of period		79,000,000	67,000,000	$ 39,000,000
Fair Value Measured on a Recurring Basis
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Derivative Asset, Current		$ 79,000,000	67,000,000
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Derivative instruments
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Electric Commodity Contract
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Derivative Asset, Current		$ 79,000,000	67,000,000
Fair Value Measured on a Recurring Basis | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		79,000,000	67,000,000
Netting	[2]	0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		79,000,000	67,000,000
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity Contract
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		79,000,000	67,000,000
Netting	[2]	0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity Contract | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity Contract | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		0	0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Electric Commodity Contract | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross		$ 79,000,000	$ 67,000,000

[1] Relates primarily to FTR instruments administered by SPP.

[2] SPS nets derivative instruments and related collateral on its balance sheet when supported by a legally enforceable master netting agreement. At Dec. 31, 2025 and 2024, derivative assets include no obligations to return cash collateral or rights to reclaim cash collateral. Counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.