v3.26.1
Fair Value Measurements - SPPC (Details) - Recurring - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Assets:    
Assets, fair value $ 6,042 $ 3,566
Investment funds    
Assets:    
Equity securities 243 283
Money market mutual funds    
Assets:    
Money market mutual funds 3,986 1,469
Level 1    
Assets:    
Assets, fair value 5,103 2,648
Level 1 | Investment funds    
Assets:    
Equity securities 243 283
Level 1 | Money market mutual funds    
Assets:    
Money market mutual funds 3,986 1,469
Level 2    
Assets:    
Assets, fair value 931 916
Level 2 | Investment funds    
Assets:    
Equity securities 0 0
Level 2 | Money market mutual funds    
Assets:    
Money market mutual funds 0 0
Level 3    
Assets:    
Assets, fair value 12 10
Level 3 | Investment funds    
Assets:    
Equity securities 0 0
Level 3 | Money market mutual funds    
Assets:    
Money market mutual funds 0 0
Commodity derivatives | Level 1    
Assets:    
Derivative asset, gross 1 0
Liabilities:    
Commodity derivatives (15) (13)
Commodity derivatives | Level 2    
Assets:    
Derivative asset, gross 41 47
Liabilities:    
Commodity derivatives (136) (169)
Commodity derivatives | Level 3    
Assets:    
Derivative asset, gross 0 2
Liabilities:    
Commodity derivatives (67) (56)
SPPC    
Assets:    
Assets, fair value 533 16
SPPC | Investment funds    
Assets:    
Equity securities 1 1
SPPC | Money market mutual funds    
Assets:    
Money market mutual funds 532 14
SPPC | Level 1    
Assets:    
Assets, fair value 533 15
SPPC | Level 1 | Investment funds    
Assets:    
Equity securities 1 1
SPPC | Level 1 | Money market mutual funds    
Assets:    
Money market mutual funds 532 14
SPPC | Level 2    
Assets:    
Assets, fair value 0 0
SPPC | Level 2 | Investment funds    
Assets:    
Equity securities 0 0
SPPC | Level 2 | Money market mutual funds    
Assets:    
Money market mutual funds 0 0
SPPC | Level 3    
Assets:    
Assets, fair value 0 1
SPPC | Level 3 | Investment funds    
Assets:    
Equity securities 0 0
SPPC | Level 3 | Money market mutual funds    
Assets:    
Money market mutual funds 0 0
SPPC | Commodity derivatives    
Assets:    
Derivative asset, gross   1
Liabilities:    
Commodity derivatives (15) (12)
SPPC | Commodity derivatives | Level 1    
Assets:    
Derivative asset, gross   0
Liabilities:    
Commodity derivatives 0 0
SPPC | Commodity derivatives | Level 2    
Assets:    
Derivative asset, gross   0
Liabilities:    
Commodity derivatives 0 0
SPPC | Commodity derivatives | Level 3    
Assets:    
Derivative asset, gross   1
Liabilities:    
Commodity derivatives $ (15) $ (12)