Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 6	$ 10	$ 16
Interest cost	24	30	78	88
Expected return on plan assets	(35)	(71)	(123)	(217)
Recognized net actuarial loss	19	48	74	149
Settlements	626	8	626	47
Net periodic benefit cost	637	21	665	83
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1		3	3
Interest cost	4	4	12	12
Recognized net actuarial loss	5	5	14	16
Amortization of prior service benefit	(4)	(3)	(11)	(11)
Settlements				26
Curtailments				(17)
Net periodic benefit cost	$ 6	$ 6	$ 18	$ 29