Employee Benefit Plans: Defined Benefit Pension Plan (Details) - PensionPlan	Dec. 31, 2025	Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Number of Defined Pension Plans	1
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%	100.00%
Return Seeking Assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	29.00%	30.00%
Liability-hedging Assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	71.00%	70.00%
Investment in privately held oil and gas company \| Return Seeking Assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	19.00%	19.00%
Real Estate \| Return Seeking Assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	5.00%	5.00%
Fixed Income \| Return Seeking Assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	3.00%	3.00%
Fixed Income \| Liability-hedging Assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	69.00%	68.00%
Hedge Funds \| Return Seeking Assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	2.00%	3.00%
Cash \| Liability-hedging Assets
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	2.00%	2.00%
Minimum \| Return Seeking Assets \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	26.00%
Minimum \| Liability-hedging Assets \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	66.00%
Maximum \| Return Seeking Assets \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	34.00%
Maximum \| Liability-hedging Assets \| Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	74.00%