v3.26.1
Fair Value Measurements - MEC (Details) - Recurring - USD ($)
$ in Millions
Mar. 31, 2026
Dec. 31, 2025
Assets:    
Derivative asset, offset $ (4) $ (8)
Assets, fair value 6,042 3,566
Liabilities:    
Derivative liability, offset 77 84
Cash collateral receivable 73 76
U.S. government obligations    
Assets:    
Debt securities 330 326
Corporate obligations    
Assets:    
Debt securities 127 133
Municipal obligations    
Assets:    
Debt securities 2 2
U.S. companies    
Assets:    
Equity securities 522 549
International companies    
Assets:    
Equity securities 9 9
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 | U.S. government obligations    
Assets:    
Debt securities 330 326
Level 1 | Corporate obligations    
Assets:    
Debt securities 0 0
Level 1 | Municipal obligations    
Assets:    
Debt securities 0 0
Level 1 | U.S. companies    
Assets:    
Equity securities 522 549
Level 1 | International companies    
Assets:    
Equity securities 9 9
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 | U.S. government obligations    
Assets:    
Debt securities 0 0
Level 2 | Corporate obligations    
Assets:    
Debt securities 127 133
Level 2 | Municipal obligations    
Assets:    
Debt securities 2 2
Level 2 | U.S. companies    
Assets:    
Equity securities 0 0
Level 2 | International companies    
Assets:    
Equity securities 0 0
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 | U.S. government obligations    
Assets:    
Debt securities 0 0
Level 3 | Corporate obligations    
Assets:    
Debt securities 0 0
Level 3 | Municipal obligations    
Assets:    
Debt securities 0 0
Level 3 | U.S. companies    
Assets:    
Equity securities 0 0
Level 3 | International companies    
Assets:    
Equity securities 0 0
Level 3 | Investment funds    
Assets:    
Equity securities 0 0
Level 3 | Money market mutual funds    
Assets:    
Money market mutual funds 0 0
Commodity derivatives    
Assets:    
Derivative asset, offset (4) (8)
Liabilities:    
Derivative liability, offset 77 83
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)
MEC    
Assets:    
Assets, fair value 1,400 1,620
Liabilities:    
Cash collateral receivable 1 5
MEC | U.S. government obligations    
Assets:    
Debt securities 287 284
MEC | Corporate obligations    
Assets:    
Debt securities 127 133
MEC | Municipal obligations    
Assets:    
Debt securities 2 2
MEC | U.S. companies    
Assets:    
Equity securities 522 548
MEC | International companies    
Assets:    
Equity securities 9 9
MEC | Investment funds    
Assets:    
Equity securities 13 20
MEC | Money market mutual funds    
Assets:    
Money market mutual funds 439 622
MEC | Level 1    
Assets:    
Assets, fair value 1,271 1,483
MEC | Level 1 | U.S. government obligations    
Assets:    
Debt securities 287 284
MEC | Level 1 | Corporate obligations    
Assets:    
Debt securities 0 0
MEC | Level 1 | Municipal obligations    
Assets:    
Debt securities 0 0
MEC | Level 1 | U.S. companies    
Assets:    
Equity securities 522 548
MEC | Level 1 | International companies    
Assets:    
Equity securities 9 9
MEC | Level 1 | Investment funds    
Assets:    
Equity securities 13 20
MEC | Level 1 | Money market mutual funds    
Assets:    
Money market mutual funds 439 622
MEC | Level 2    
Assets:    
Assets, fair value 130 138
MEC | Level 2 | U.S. government obligations    
Assets:    
Debt securities 0 0
MEC | Level 2 | Corporate obligations    
Assets:    
Debt securities 127 133
MEC | Level 2 | Municipal obligations    
Assets:    
Debt securities 2 2
MEC | Level 2 | U.S. companies    
Assets:    
Equity securities 0 0
MEC | Level 2 | International companies    
Assets:    
Equity securities 0 0
MEC | Level 2 | Investment funds    
Assets:    
Equity securities 0  
MEC | Level 2 | Money market mutual funds    
Assets:    
Money market mutual funds 0 0
MEC | Level 3    
Assets:    
Assets, fair value 0 1
MEC | Level 3 | U.S. government obligations    
Assets:    
Debt securities 0 0
MEC | Level 3 | Corporate obligations    
Assets:    
Debt securities 0 0
MEC | Level 3 | Municipal obligations    
Assets:    
Debt securities 0 0
MEC | Level 3 | U.S. companies    
Assets:    
Equity securities 0 0
MEC | Level 3 | International companies    
Assets:    
Equity securities 0 0
MEC | Level 3 | Investment funds    
Assets:    
Equity securities 0  
MEC | Level 3 | Money market mutual funds    
Assets:    
Money market mutual funds 0 0
MEC | Commodity derivatives    
Assets:    
Derivative asset, gross 1 2
Derivative asset, offset (1) (2)
Liabilities:    
Commodity derivatives (7) (14)
Derivative liability, offset 2 7
MEC | Commodity derivatives | Level 1    
Assets:    
Derivative asset, gross 1 0
Liabilities:    
Commodity derivatives 0 0
MEC | Commodity derivatives | Level 2    
Assets:    
Derivative asset, gross 1 3
Liabilities:    
Commodity derivatives (8) (18)
MEC | Commodity derivatives | Level 3    
Assets:    
Derivative asset, gross 0 1
Liabilities:    
Commodity derivatives $ (1) $ (3)