Employee Benefits - Components of Net Periodic Benefit Cost and Other Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Pension Plans [Member]
Components Of Net Periodic Benefit Cost
Service cost	$ 69	$ 66	$ 206	$ 198
Interest cost	62	54	185	164
Expected return on plan assets	(119)	(112)	(358)	(337)
Prior service cost (credit) amortization	(1)		(2)	(1)
Actuarial loss (gain) amortization	35	42	105	127
Net periodic benefit cost	46	50	136	151
Postretirement Welfare Plan [Member]
Components Of Net Periodic Benefit Cost
Interest cost		1		1
Prior service cost (credit) amortization		(1)	(2)	(3)
Actuarial loss (gain) amortization	(2)	(2)	(5)	(5)
Net periodic benefit cost	$ (2)	$ (2)	$ (7)	$ (7)