Segment Information - Reconciliation of Operating Revenues (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	$ 32,596	$ 33,789	$ 65,508	$ 67,343
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	32,041	33,230	64,392	66,231
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	621	623	1,238	1,241
Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating revenues	$ (66)	$ (64)	$ (122)	$ (129)