v3.25.0.1
Benefit Plans: (Components of Net Periodic Benefit Cost) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension      
Defined Benefit Plan Disclosure [Line Items]      
Service cost $ 218 $ 174 $ 233
Interest cost 234 258 78
Expected return on plan assets (403) (365) (352)
Amortization:      
Net losses 93 18 181
Prior service cost (credit) (2) (2) (2)
Net transition obligation 0 0 0
Settlement and curtailment 2 7 2
Net periodic pension and postretirement costs 142 90 140
Post- retirement      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 3 4 2
Interest cost 13 12 6
Expected return on plan assets 0 0 0
Amortization:      
Net losses (1) (1) 2
Prior service cost (credit) 0 0 0
Net transition obligation 0 0 0
Settlement and curtailment 1 1 2
Net periodic pension and postretirement costs $ 16 $ 16 $ 12