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Asset retirement obligations ('ARO') (Tables)

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

Schedule of changes in asset retirement obligations

The reconciliation of the changes in the asset retirement obligations is presented below:

	Year ended December 31,
	2017				2016
Beginning balance, ARO liability	$	35,418			$	35,165
Additional ARO liability incurred	1,354				1,272
ARO liabilities settled	(9,900		)		(1,930		)
Accretion expense	1,924				1,903
Adjustments	(278		)		(992		)
Ending balance, ARO liability	$	28,518			$	35,418

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- References

No definition available.

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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

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