Segment Information - Summary of Reconciliation of Segment Operating Revenues (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating Revenues	$ 133,613	$ 128,292	$ 131,868
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating Revenues	126,342	119,495	122,499
Corporate and other
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating Revenues	7,722	9,334	9,812
Eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Operating Revenues	$ (451)	$ (537)	$ (443)