Employee Benefits - Cost Allocation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Affiliated Entity
Employee Benefits
Allocated expenses by parent entities (as a percent)	79.00%	86.00%	87.00%
Pension, Supplemental and Other Postretirement Benefit Plans | Affiliated Entity
Employee Benefits
Pension settlement term	30 years
Revenue from affiliate	$ 48	$ 52
Pension Plan
Employee Benefits
Defined benefit plan, service cost	17	20	$ 22
Post-Retirement Benefit Plan
Employee Benefits
Defined benefit plan, service cost	$ 3	$ 4	$ 4