Employee Retirement Benefits - Components of Net Periodic Costs for Qualified and Supplemental Pension Plans (Details) - Qualified Pension Plans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan Disclosure
Service cost	$ 1	$ 1
Interest cost	3	3
Expected return on plan assets	(5)	(5)
Amortization of actuarial loss and prior service cost	0	(1)
Other	0	(5)
Total non-service benefit	(2)	(8)
Net periodic benefit cost	$ (1)	$ (7)