v3.26.1
Accumulated Other Comprehensive Income (Loss), Net of Tax - Schedule of Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Accumulated Other Comprehensive Income (Loss) [Roll Forward]      
Beginning Balance $ 16,982 $ 16,114 $ 16,114
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) 12 2  
Other Comprehensive Income (Loss), net of tax 6 (3)  
Ending Balance 17,303 16,370 16,982
Cash Flow Hedges [Member]      
Accumulated Other Comprehensive Income (Loss) [Roll Forward]      
Beginning Balance 24 36 36
Other Comprehensive Income (Loss) before Reclassifications 4 (20) (8)
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) (1) 0 (4)
Other Comprehensive Income (Loss), net of tax 3 (20)  
Ending Balance 27 16 24
Pension and OPEB Plans [Member]      
Accumulated Other Comprehensive Income (Loss) [Roll Forward]      
Beginning Balance (56) (76) (76)
Other Comprehensive Income (Loss) before Reclassifications 0 0  
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) 1 1  
Other Comprehensive Income (Loss), net of tax 1 1  
Ending Balance (55) (75) (56)
Available-for-Sale Securities [Member]      
Accumulated Other Comprehensive Income (Loss) [Roll Forward]      
Beginning Balance (59) (93) (93)
Other Comprehensive Income (Loss) before Reclassifications (10) 15  
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) 12 1  
Other Comprehensive Income (Loss), net of tax 2 16  
Ending Balance (57) (77) (59)
AOCI Attributable to Parent [Member]      
Accumulated Other Comprehensive Income (Loss) [Roll Forward]      
Beginning Balance (91) (133) (133)
Other Comprehensive Income (Loss) before Reclassifications (6) (5)  
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) 12 2  
Other Comprehensive Income (Loss), net of tax 6 (3)  
Ending Balance $ (85) $ (136) $ (91)