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Employee Benefit Plans: Fair Value Measurements (Details) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Hedge Funds | Minimum |  |  |
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 |  |
Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 458,387 | $ 473,721 | $ 434,284
Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 458,387 | 473,721 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 415,490 | 441,966 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 42,897 | 31,755 |
Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 7,972 | 8,165 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 7,972 | 8,165 |
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 | 7,972 | 8,165 |
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 415,490 | 441,966 |
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 | 0 |
Common Collective Trust, Cash And Cash Equivalents | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 6,009 | 16,810 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 6,009 | 16,810 |
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 | 6,009 | 16,810 |
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 Fund | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 70,262 | 100,311 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 70,262 | 100,311 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 0 | 0 |
Common Collective Trust, Equity Fund | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust, Equity Fund | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 70,262 | 100,311 |
Common Collective Trust, Equity Fund | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust, Fixed Income Fund | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 339,219 | 324,845 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 339,219 | 324,845 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 0 | 0 |
Common Collective Trust, Fixed Income Fund | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Common Collective Trust, Fixed Income Fund | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 339,219 | 324,845 |
Common Collective Trust, Fixed Income Fund | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Real Estate Funds | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 30,407 | 14,301 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 0 | 0 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 30,407 | 14,301 |
Real Estate Funds | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Real Estate Funds | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | 0 | 0 |
Real Estate Funds | Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 0 | 0 |
Hedge Funds | Minimum |  |  |
Percentage Of Monthly Redemption | 10.00% |  |
Hedge Funds | Fair Value, Measurements, Recurring | Pension Plan |  |  |
Defined Benefit Plan, Plan Assets, Amount | $ 12,490 | 17,454 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 0 | 0 |
Defined Benefit Plan, Alternative Investments, Fair Value Of Plan Assets | 12,490 | 17,454 |
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 | 7,972 | 8,165 |
Defined Benefit Plan, Fair Value of Plan Assets, Excluding Net Asset Value investments | 7,972 | 8,165 |
Cash | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Postretirement Health Coverage |  |  |
Defined Benefit Plan, Plan Assets, Amount | 7,972 | 8,165 |
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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