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
	Mar. 31, 2023	Mar. 31, 2022
Pension Plans [Member]
Components Of Net Periodic Benefit Cost
Service cost	$ 56	$ 69
Interest cost	93	61
Expected return on plan assets	(137)	(119)
Prior service cost (credit) amortization		(1)
Actuarial loss (gain) amortization	1	35
Net periodic benefit cost	13	45
Postretirement Welfare Plan [Member]
Components Of Net Periodic Benefit Cost
Interest cost	1
Expected return on plan assets	(1)
Prior service cost (credit) amortization	(1)
Actuarial loss (gain) amortization	(2)	(2)
Net periodic benefit cost	$ (3)	$ (2)