v3.24.0.1
Benefit Plans: (Components of Net Periodic Benefit Cost) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Service cost $ 174 $ 233 $ 291
Interest cost 258 78 50
Expected return on plan assets (365) (352) (371)
Amortization:      
Net losses 18 181 314
Prior service cost (credit) (2) (2) 1
Net transition obligation 0 0 0
Settlement and curtailment 7 2 5
Net periodic pension and postretirement costs 90 140 290
Postretirement      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 4 2 2
Interest cost 12 6 5
Expected return on plan assets 0 0 0
Amortization:      
Net losses (1) 2 3
Prior service cost (credit) 0 0 0
Net transition obligation 0 0 0
Settlement and curtailment 1 2 0
Net periodic pension and postretirement costs $ 16 $ 12 $ 10