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Employee Benefit Plans: Fair Value Measurements (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 323,141 | $ 458,387 | $ 473,721
Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 323,142 | 458,387 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 293,486 | 415,490 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 29,656 | 42,897 |
Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 7,752 | 7,972 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 7,752 | 7,972 |
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 7,752 | 7,972 |
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 293,486 | 415,490 |
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 |  |
Common Collective Trust, Cash And Cash Equivalents | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 6,374 | 6,009 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 6,374 | 6,009 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 0 | 0 |
Common Collective Trust, Cash And Cash Equivalents | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust, Cash And Cash Equivalents | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 6,374 | 6,009 |
Common Collective Trust, Cash And Cash Equivalents | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust - Equity | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 45,087 | 70,262 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 45,087 | 70,262 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 0 | 0 |
Common Collective Trust - Equity | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust - Equity | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 45,087 | 70,262 |
Common Collective Trust - Equity | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust - Fixed Income | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 242,025 | 339,219 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 242,025 | 339,219 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 0 | 0 |
Common Collective Trust - Fixed Income | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust - Fixed Income | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 242,025 | 339,219 |
Common Collective Trust - Fixed Income | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust - Real Estate | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 21,572 | 30,407 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments |  | 0 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 21,572 | 30,407 |
Common Collective Trust - Real Estate | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust - Real Estate | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 0 | 0 |
Common Collective Trust - Real Estate | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount |  | 0 |
Hedge Funds | Minimum |  |  |
Percentage Of Monthly Redemption | 10.00% |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period | 15 days |  |
Hedge Funds | Maximum |  |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period | 60 days |  |
Hedge Funds | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 8,084 | 12,490 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments |  | 0 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 8,084 | 12,490 |
Hedge Funds | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Hedge Funds | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Hedge Funds | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Cash | Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 7,752 | 7,972 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 7,752 | 7,972 |
Cash | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 7,752 | 7,972 |
Cash | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Cash | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 0 | $ 0 |

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