Benefit Plans: (Weighted-Average Assumptions to Determine Benefit Obligations) (Details)	Dec. 31, 2025	Dec. 31, 2024
Pension
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	2.42%	2.07%
Rate of compensation increase (as a percent)	1.85%	1.89%
Interest crediting rate (as a percent)	3.16%	3.05%
Post- retirement
Defined Benefit Plan Disclosure [Line Items]
Discount rate (as a percent)	5.56%	5.35%
Heath care cost trend rate assumed for next year (as a percent)	6.67%	6.82%
Ultimate trend rate (as a percent)	4.60%	4.71%