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Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations
Asset Retirement Obligations
The following table reconciles our AROs as of the dates presented, which are included in the Other liabilities caption on our Consolidated Balance Sheets: 
 
As of December 31,
 
2015
 
2014
Balance at beginning of year
$
5,890

 
$
6,437

Changes in estimates
172

 
112

Liabilities incurred
110

 
238

Liabilities settled
—

 
(92
)
Sale of properties
(3,932
)
 
(1,224
)
Accretion expense
381

 
419

Balance at end of year
$
2,621

 
$
5,890