Segment Information - Reconciliation of Operating Revenues (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	$ 32,912	$ 33,554
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	32,351	33,001
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	617	618
Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	$ (56)	$ (65)