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v3.19.1

Asset Retirement Obligation (Tables) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 | Dec. 31, 2018
ASSET RETIREMENT OBLIGATION |  |
Summary of Asset Retirement Obligation | The following table summarizes the changes in the reserve for future restoration and reclamation costs on the balance sheet:
|  | March 31, |  | December 31,
(thousands of dollars) |  | 2019 |  | 2018
Balance, beginning of period |  | $ | 6,203 |  | $ | 5,731
Liabilities settled |  |  | (335) |  |  | (521)
Accretion expense |  |  | 126 |  |  | 993
Balance, end of period |  |  | 5,994 |  |  | 6,203
Less: Current portion |  |  | (894) |  |  | (708)
Non-current portion |  | $ | 5,100 |  | $ | 5,495
| Changes to the Company’s asset retirement obligation are summarized below:
|  | December 31, |  |  | December 31, |
|  | 2018 |  |  | 2017 |
|  | (thousands of dollars) |
Balance, beginning of period |  | $ | 5,731 |  |  | $ | 4,789 |
Liabilities settled |  |  | (521 | ) |  |  | (97 | )
Accretion expense |  |  | 993 |  |  |  | 1,039 |
Balance, end of period |  |  | 6,203 |  |  |  | 5,731 |
Less: Included in liabilities held for sale |  |  | - |  |  |  | - |
Less: Current portion |  |  | (708 | ) |  |  | (1,078 | )
Non-current portion |  | $ | 5,495 |  |  | $ | 4,653 |

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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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