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ASSET RETIREMENT OBLIGATION: (Tables)

12 Months Ended

Dec. 31, 2014

ASSET RETIREMENT OBLIGATION:

Summary of the asset retirement obligation activity

The following table summarizes the asset retirement obligation activity for years ended December 31, 2014 and 2013 (in millions):

		2014			2013
Balance as of January 1		$	124.8		$	122.3
Changes in estimates		(9.6		)	—
Additions		—			—
Closure payments		(12.2		)	(6.3		)
Accretion expense		13.1			8.8
Balance as of December 31,		$	116.1		$	124.8

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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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