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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2023
Asset Retirement Obligation [Abstract] |
Changes to Asset Retirement Obligation | The following table describes changes to the asset retirement obligation liability (dollars in millions):
|  | Year Ended December 31, |
|  | 2023 |  |  | 2022 |
Asset retirement obligation at beginning of period |  | $ | 30.2 |  |  | $ | 29.4 |
Accretion expense |  |  | 1.6 |  |  |  | 1.3 |
Liabilities incurred |  |  | 0.1 |  |  |  | — |
Payments |  |  | (0.4 | ) |  |  | (0.3 | )
Revisions in estimated cash flows |  |  | (0.1 | ) |  |  | (0.2 | )
Asset retirement obligation at end of period |  | $ | 31.4 |  |  | $ | 30.2 |

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- Definition Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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