v3.25.2
Transactions Involving Related Parties - Summary of Income Statement Impact of Transactions with Parent and Affiliated Companies (Detail) - USD ($)
$ in Millions
3 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Revenue:    
Subsidy income $ 2,598 $ 2,243
General and administrative expenses:    
Lease expense 2 2
Affiliated Entity    
Revenue:    
Subsidy income 338 249
General and administrative expenses:    
Support Compensation Agreement fees 23 20
Benefit plan expenses 2 1
Shared services 19 19
Lease expense 1 1
Related Party    
Interest expense:    
Related party debt $ 20 $ 0