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Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of Reconciliation of Changes in the Asset Retirement Obligations
The reconciliation of changes in the asset retirement obligations at December 31, 2017 and 2016 is as follows:
 
 
As of December 31,
 
 
2017
 
2016
Balance at beginning of period
 
$
272,538

 
$
288,977

Accretion expense
 
18,922

 
20,111

Payments
 
(10,467
)
 
(11,637
)
Revisions in estimated cash flows
 
(20,529
)
 
(25,427
)
Other
 
(1,641
)
 
514

Balance at end of period
 
$
258,823

 
$
272,538