Retirement and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Pension benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 1
Interest cost	16	19
Expected return on plan assets	(14)	(17)
Recognized net actuarial (gain) loss	9	7
Net periodic cost (benefit)	11	10
Other postretirement benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	1	1
Recognized net actuarial (gain) loss	(2)	(2)
Amortization of prior service benefit	(2)	(2)
Net periodic cost (benefit)	$ (3)	$ (3)