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ASSET RETIREMENT OBLIGATION: (Tables)

3 Months Ended

Mar. 31, 2024

ASSET RETIREMENT OBLIGATION:

Summary of asset retirement obligation activity

The following table summarizes the asset retirement obligation activity for the three-month period ended March 31, 2024 and 2023 (in millions):

​	​	​	​	​	​	​
​		2024			2023
Balance as of January 1	​	$	612.5	​	$	585.3
Changes in estimates	​		(2.3)	​		—
Closure payments	​		—	​		(0.2)
Accretion expense	​		7.6	​		6.4
Balance as of March 31,	​	$	617.8	​	$	591.5

​

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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/2009/role/commonPracticeRef
-Topic 410
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481850/410-20-50-1

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