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Financing: Long-Term Debt: Debt Transactions (Details) - USD ($) $ in Thousands | Aug. 26, 2021 | Jun. 17, 2020 | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | --- | --- | ---
Debt Instrument [Line Items] |  |  |  |
Less unamortized deferred financing costs |  |  | $ 26,878 | $ 24,809
Senior Unsecured Notes Due 2024 |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Stated interest rate (percent) | 1.037% |  |  |
Debt Instrument, Term | 3 years |  |  |
Less unamortized deferred financing costs | $ 3,700 |  |  |
Corporate, Non-Segment | Senior Unsecured Notes Due 2024 |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Proceeds from Issuance of Debt |  | $ 600,000 |  |
Corporate, Non-Segment | Senior Unsecured Notes Due 2030 |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Proceeds from Issuance of Debt |  | $ 400,000 |  |
Stated interest rate (percent) |  | 2.50% |  |
Long-term Debt, Term |  | 10 years |  |

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- Definition Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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