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ASSET RETIREMENT OBLIGATIONS (Tables)
 12 Months Ended
Dec. 31, 2019
Asset Retirement Obligation [Abstract]  
Asset retirement obligations

The following table describes the changes to the Company’s asset retirement obligations liability for the following periods:
 
Year Ended December 31,
 
2019
 
2018
 
2017
 
(in millions)
Asset retirement obligations, beginning of period
$
136

 
$
21

 
$
17

Additional liabilities incurred
8

 
3

 
2

Liabilities acquired
4

 
111

 
2

Liabilities settled
(61
)
 
(2
)
 
(1
)
Accretion expense
7

 
2

 
1

Revisions in estimated liabilities
—

 
1

 
—

Asset retirement obligations, end of period
94

 
136

 
21

Less current portion
—

 
—

 
1

Asset retirement obligations - long-term
$
94

 
$
136

 
$
20