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Asset Retirement Obligations Asset Retirement Obligations (Tables)
12 Months Ended
Dec. 31, 2012
Asset Retirement Obligations [Abstract]  
Schedule of Change in Asset Retirement Obligation [Table Text Block]
The following table describes the changes to the Company's asset retirement obligation liability:
 
Year Ended December 31
 
2012
 
2011
 
(In thousands)
Balance at January 1 (including current portion)
$
473,903

 
$
343,119

Accretion expense
39,020

 
33,601

Obligations incurred or acquired

 
115,019

Adjustments to the liability from changes in estimates
4,400

 
11,176

Liabilities settled
(68,698
)
 
(29,012
)
Balance at December 31
$
448,625

 
$
473,903

Current portion included in accrued expenses
(38,920
)
 
(27,119
)
Noncurrent liability
$
409,705

 
$
446,784