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ASSET RETIREMENT OBLIGATIONS
 12 Months Ended
Dec. 31, 2019
Asset Retirement Obligation [Abstract]  
ASSET RETIREMENT OBLIGATIONS ASSET RETIREMENT OBLIGATIONS

The changes in the carrying amount of the Company’s asset retirement obligations were as follows:
 
2019
 
2018
Beginning balance as of January 1,
$
1,210.0

 
$
1,175.3

Additions
61.8

 
39.6

Accretion expense
81.6

 
83.6

Revisions in estimates (1)
56.8

 
(81.5
)
Settlements
(26.1
)
 
(7.0
)
Balance as of December 31,
$
1,384.1

 
$
1,210.0

 
_______________
(1)
Revisions in estimates include decreases to the liability of $6.7 million and $49.4 million related to foreign currency translation for the years ended December 31, 2019 and 2018, respectively.

As of December 31, 2019, the estimated undiscounted future cash outlay for asset retirement obligations was $3.2 billion.