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Accounting for Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2017
Accounting for Asset Retirement Obligations [Abstract] |
Reconciliation of asset retirement obligations | The following is a reconciliation of asset retirement obligations as of December 31, 2017 and 2016:
|  | 2017 |  |  | 2016 |
|  | (millions of dollars) |
Asset retirement liability, beginning of period |  | $ | 21.5 |  |  | $ | 21.4 |
Accretion expense |  |  | 3.3 |  |  |  | 2.5 |
Payments |  |  | (3.2 | ) |  |  | (1.6 | )
Foreign currency translation |  |  | 0.5 |  |  |  | (0.8 | )
Asset retirement liability, end of period |  | $ | 22.1 |  |  | $ | 21.5 |

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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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