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ASSET RETIREMENT OBLIGATION: (Tables)

3 Months Ended

Mar. 31, 2013

ASSET RETIREMENT OBLIGATION:

Summary of the asset retirement obligation activity

The following table summarizes the asset retirement obligation activity for the three months ended March 31, 2013 and 2012 (in millions):

		2013			2012
Balance as of January 1		$	118.2		$	62.0
Changes in estimates		—			—
Additions		—			—
Accretion expense		1.8			0.8
Balance as of March 31,		$	120.0		$	62.8

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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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