v3.26.1
Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Defined Benefit Plan Disclosure [Line Items]      
Net periodic benefit cost $ 5 $ 0 $ 3
Pension Benefits [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 24 23 23
Interest cost 71 78 76
Expected return on assets (79) (80) (77)
Amortization — losses (gains), net (gains (losses), net) 4 3 (1)
Amortization — prior service credit (2) (2) (2)
Settlement/curtailment (gain) loss 0 1 0
Net periodic benefit cost 18 23 19
Proportionate share of non-consolidated affiliates' pension costs 5 4 4
Total net periodic benefit cost recognized 23 27 23
Other Benefits [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 2 3 3
Interest cost 7 7 7
Expected return on assets 0 0 0
Amortization — losses (gains), net (gains (losses), net) (3) (3) (3)
Amortization — prior service credit (3) (4) (3)
Settlement/curtailment (gain) loss (11) 0 0
Net periodic benefit cost (8) 3 4
Proportionate share of non-consolidated affiliates' pension costs 0 0 0
Total net periodic benefit cost recognized $ (8) $ 3 $ 4