Regulatory Matters - SPPC - Regulatory Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 7,033	$ 6,818
Regulatory liabilities, noncurrent	$ 6,754	6,644
Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	27 years
Total regulatory liabilities	$ 2,918	2,741
Other
Regulatory Liabilities [Line Items]
Total regulatory liabilities	406	296
SPPC
Regulatory Liabilities [Line Items]
Total regulatory liabilities	522	439
Regulatory liabilities, current	106	15
Regulatory liabilities, noncurrent	416	424
SPPC | Deferred income taxes
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 193	206
SPPC | Cost of removal
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	31 years
Total regulatory liabilities	$ 216	211
SPPC | Deferred energy costs
Regulatory Liabilities [Line Items]
Regulatory liability, amortization period	1 year
Total regulatory liabilities	$ 86	0
SPPC | Other
Regulatory Liabilities [Line Items]
Total regulatory liabilities	$ 27	$ 22