Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 5
Interest cost	27	29
Expected return on plan assets	(44)	(73)
Recognized net actuarial loss	28	51
Net periodic benefit cost	14	12
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	2
Interest cost	4	4
Recognized net actuarial loss	4	6
Amortization of prior service cost	(3)	(4)
Settlements		26
Curtailments		(17)
Net periodic benefit cost	$ 6	$ 17