Employee Benefit Plans: Fair Value Employee Benefit Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Beginning fair value of plan assets	$ 473,721	$ 434,284
Investment income (loss)	20,165	64,006
Employer contributions	0	12,700
Retiree contributions	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	(35,499)	(37,269)
Ending fair value of plan assets	458,387	473,721
Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Beginning fair value of plan assets	0	0
Investment income (loss)	0	0
Employer contributions	2,576	2,674
Retiree contributions	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	(2,576)	(2,674)
Ending fair value of plan assets	0	0
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Beginning fair value of plan assets	8,165	8,305
Investment income (loss)	(35)	33
Employer contributions	4,726	4,374
Retiree contributions	1,548	1,511
Defined Benefit Plan, Plan Assets, Benefits Paid	(6,432)	(6,058)
Ending fair value of plan assets	$ 7,972	$ 8,165

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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- Definition

Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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- Definition

Amount of contributions received by defined benefit plan from participant which increases plan assets.

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