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Asset Retirement Obligation (Tables) | 12 Months Ended
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Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract] |
Schedule of Change in Asset Retirement Obligation | The table below summarizes the changes in our recorded asset retirement obligations (in thousands):
| Year Ended December 31,
| 2018 |  | 2017 |  | 2016
Beginning balance | $ | 9,103 |  |  | $ | 9,042 |  |  | $ | 8,909 |
Obligations acquired | 487 |  |  | — |  |  | — |
Accretion expense | 395 |  |  | 369 |  |  | 362 |
Liabilities settled during period | — |  |  | (308 | ) |  | (229 | )
Ending balance | $ | 9,985 |  |  | $ | 9,103 |  |  | $ | 9,042 |

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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/2003/role/presentationRef -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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