Employee Retirement Benefits - Components of Net Periodic Costs for Qualified and Supplemental Pension Plans (Details) - Qualified Pension Plans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure
Service cost	$ 1	$ 2	$ 4	$ 7
Interest cost	3	3	9	8
Expected return on plan assets	(5)	(6)	(15)	(17)
Amortization of actuarial loss and prior service cost	0	0	(2)	0
Other	0	0	(5)	0
Total non-service benefit	(2)	(3)	(13)	(9)
Net periodic benefit cost	$ (1)	$ (1)	$ (9)	$ (2)