ASSET RETIREMENT OBLIGATION (Tables)
 9 Months Ended
Sep. 30, 2016
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of Changes to Asset Retirement Obligation
Following is a table of the changes to our asset retirement obligation for the following periods (in thousands):
 
 
Three Months Ended September 30,
 
Nine Months Ended September 30,
 
 
2016
 
2015
 
2016
 
2015
Asset retirement obligation, at beginning of period
 
$
23,832

 
$
22,869

 
$
22,951

 
$
22,037

Liabilities settled
 
—

 
(70
)
 
(3
)
 
(86
)
Liabilities incurred
 
—

 
—

 
—

 
—

Changes in estimated obligations
 
—

 
—

 
—

 
—

Accretion of discount
 
442

 
424

 
1,326

 
1,272

Total asset retirement obligation, at end of period
 
$
24,274

 
$
23,223

 
$
24,274

 
$
23,223