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Asset Retirement Obligations (Tables)
3 Months Ended
Mar. 31, 2013
Asset Retirement Obligation [Abstract]  
Activity Associated With Asset Retirement Obligations
The following table illustrates the activity associated with our asset retirement obligations for the three months ended March 31, 2013 and March 31, 2012.
(in thousands)
 
2013
 
2012
Asset retirement obligations, January 1
 
$
2,800

 
$
3,297

Accretion expense
 
30

 
43

Liabilities settled
 
(297
)
 
(128
)
Changes in expected cash flows and timing
 
185

 
98

Asset retirement obligations, March 31
 
$
2,718

 
$
3,310