Segment Information - Reconciliation of Operating Revenues (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	$ 33,485	$ 32,981
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	32,904	32,433
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	660	611
Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	$ (79)	$ (63)