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Nature of Operations And Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($)
Basis Of Accounting Presentation [Line Items] |  |  |
Number of customers | 3,800,000 |  |
Other than Temporary Impairment Losses, Investments | $ 0.0 | $ 0.0 | $ 0.0
Pre-tax rate for allowance for funds used during construction | 3.90% | 3.40% | 3.30%
Inventory valued using LIFO | $ 43.9 | $ 43.0 |
Excess of replacement over LIFO value | (22.5) | (7.7) |
Inventory valued using the weighted average cost methodology | $ 222.0 | $ 488.7 |

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- Definition The excess of replacement or current cost over the stated LIFO (last in first out) inventory value when the LIFO inventory method is utilized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(6)(c)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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