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Asset Retirement Obligations (Tables)
9 Months Ended
Sep. 30, 2011
Asset Retirement Obligations [Abstract] 
Changes in ARO
Changes in Questar's ARO from the Consolidated Balance Sheets for the nine months ended September 30 were as follows:

 
2011
2010
 
(in millions)
ARO liability at December 31
$60.9 
$65.0 
Accretion
2.3 
2.1 
Liabilities incurred
0.9 
0.7 
Revisions
2.4 
(8.2)
Liabilities settled
(2.0)
(0.2)
ARO liability at September 30
$64.5 
$59.4