Employee Benefits - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 56	$ 68	$ 112	$ 137
Interest cost	93	62	185	123
Expected return on plan assets	(137)	(120)	(273)	(239)
Prior service cost (credit) amortization			(1)	(1)
Actuarial loss (gain) amortization	1	35	2	70
Net periodic benefit cost	13	45	25	90
Postretirement Welfare Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1		1
Expected return on plan assets	(1)		(1)
Prior service cost (credit) amortization	(1)	(2)	(1)	(2)
Actuarial loss (gain) amortization	(2)	(1)	(4)	(3)
Net periodic benefit cost	$ (3)	$ (3)	$ (5)	$ (5)