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Employee Benefit Plans: Plan Contributions (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items] |  |  |
Payment for Pension Benefits | $ 0 | $ 12,700 | $ 12,700
Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Payment for Pension Benefits | 0 | 12,700 |
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year | 3,900 |  |
Other Postretirement Benefits Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Payment for Pension and Other Postretirement Benefits | 6,432 | 6,058 |
Supplemental Employee Retirement Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Payment for Pension and Other Postretirement Benefits | 2,576 | 2,674 |
Defined Contribution Plan, Company Retirement |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Contribution Plan, Employer Discretionary Contribution Amount | 11,332 | 10,455 |
Defined Contribution Plan, 401K |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Contribution Plan, Employer Discretionary Contribution Amount | $ 15,938 | $ 15,240 |

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- Definition Amount of cash outflow for other postretirement benefit. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree. Excludes pension benefit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3536-108585 + Details
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