XML 48 R31.htm IDEA: XBRL DOCUMENT v3.3.1.900
Asset Retirement Obligation (Tables)
 12 Months Ended
Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]  
Changes to the Company's asset retirement obligation liability
The following table describes the changes to the Company’s asset retirement obligation (in thousands):
 
Year Ended December 31,
 
2015
 
2014
Asset retirement obligation, beginning of period
$
54,970

 
$
48,536

Liabilities incurred
466

 
756

Liabilities settled
(5,002
)
 
(3,623
)
Accretion expense
3,259

 
2,958

Revisions in estimated cash flows
(11,137
)
 
6,343

Asset retirement obligation, end of period
42,556

 
54,970

Less: current portion of asset retirement obligation
(6,015
)
 
(2,756
)
Long-term asset retirement obligation
$
36,541

 
$
52,214