Pension and Other Postretirement Benefits - Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pension
Components of net periodic benefit cost:
Service cost	$ 9	$ 11	$ 27	$ 35
Interest cost	24	13	70	38
Expected return on plan assets	(33)	(24)	(97)	(76)
Amortization of actuarial loss (gain)	0	5	2	18
Amortization of prior service cost	1	1	1	1
Settlements	0	1	0	1
Total net periodic benefit cost (income)	1	7	3	17
Other Postretirement Benefits
Components of net periodic benefit cost:
Service cost	1	2	3	5
Interest cost	5	3	17	10
Expected return on plan assets	(5)	(7)	(16)	(20)
Amortization of actuarial loss (gain)	(1)	(1)	(3)	(3)
Amortization of prior service cost	0	0	0	0
Settlements	0	0	0	0
Total net periodic benefit cost (income)	$ 0	$ (3)	$ 1	$ (8)