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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2020
Asset Retirement Obligation Disclosure [Abstract] |
Schedule of changes in asset retirement obligations | The reconciliation of the changes in our AROs is presented below:
| Year ended December 31,
| 2020 |  | 2019
Beginning balance, ARO liability | $ | 18.9 |  |  | $ | 18.2 |
Additional ARO liability incurred | 2.3 |  |  | 2.9 |
ARO liabilities settled | (2.2) |  |  | (3.5) |
Accretion expense | 1.3 |  |  | 1.3 |
Revisions in estimated cash flows | (0.5) |  |  | — |
Ending balance, ARO liability | $ | 19.8 |  |  | $ | 18.9 |

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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859 + Details
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