XML 89 R42.htm IDEA: XBRL DOCUMENT v3.25.0.1
ASSET RETIREMENT OBLIGATION: (Tables)
12 Months Ended
Dec. 31, 2024
ASSET RETIREMENT OBLIGATION:  
Summary of asset retirement obligation activity

The following table summarizes the asset retirement obligation activity for the years ended December 31, 2024 and 2023 (in millions):

    

2024

    

2023

Balance as of January 1

$

612.5

$

585.3

Changes in estimates

 

(116.6)

 

0.2

Additions

 

24.6

 

1.0

Closure payments

 

 

(0.3)

Accretion expense

 

25.7

 

26.3

Balance as of December 31, 

$

546.1

$

612.5