Short-term Debt and Credit Facilities - SPPC (Details)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Line of Credit Facility [Line Items]
Line of credit, maximum capacity	$ 10,705,000,000	$ 10,873,000,000
Short-term debt	4,148,000,000	1,119,000,000
SPPC
Line of Credit Facility [Line Items]
Short-term debt	$ 0	0
SPPC | Line of credit
Line of Credit Facility [Line Items]
Debt to capitalization ratio	0.65
SPPC | Secured credit facility, $400 million, expiring June 2026
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 0
SPPC | Secured credit facility, $400 million, expiring June 2026 | Line of credit
Line of Credit Facility [Line Items]
Line of credit, maximum capacity	400,000,000
SPPC | Secured credit facility, $400 million, expiring June 2026 | Letter of credit
Line of Credit Facility [Line Items]
Line of credit, maximum capacity	$ 50,000,000
SPPC | Secured credit facility, $250 million, expiring June 2025
Line of Credit Facility [Line Items]
Letters of credit outstanding		0
SPPC | Secured credit facility, $250 million, expiring June 2025 | Line of credit
Line of Credit Facility [Line Items]
Line of credit, maximum capacity		250,000,000
SPPC | Secured credit facility, $250 million, expiring June 2025 | Letter of credit
Line of Credit Facility [Line Items]
Line of credit, maximum capacity		$ 75,000,000