Employee Retirement Benefits - Components of Net Periodic Costs for Qualified and Supplemental Pension Plans (Detail) - Qualified Pension Plans - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Defined Benefit Plan Disclosure
Service cost	$ 3	$ 3	$ 5	$ 5
Interest cost	2	3	5	5
Expected return on plan assets	(5)	(6)	(11)	(11)
Amortization of actuarial loss and prior service cost	0	1	0	3
Other	0	0	0	2
Total non-service benefit	(3)	(2)	(6)	(1)
Net periodic benefit cost	$ 0	$ 1	$ (1)	$ 4