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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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