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Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2013
Asset Retirement Obligations [Abstract]  
Reconciliation Of Beginning And Ending Aggregate Carrying Amount Of Asset Retirement Obligation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

December 31,

(Thousands of dollars)

 

2013

 

2012

Balance at beginning of period

 

$
15,401 

 

 
13,190 

Accretion expense

 

 
1,096 

 

 
980 

Liabilities incurred

 

 
633 

 

 
1,231 

Balance at end of period

 

$
17,130 

 

 
15,401