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Accounting for Asset Retirement Obligations (Tables)
 9 Months Ended
Sep. 30, 2012
Accounting for Asset Retirement Obligations [Abstract]  
Reconciliation of Asset Retirement Obligations
     The following is a reconciliation of asset retirement obligations as of September 30, 2012:

(millions of dollars)
 
 
 
Asset retirement liability, December 31, 2011
$
14.7
 
Accretion expense                                                                                            
 
0.5
 
Payments                                                                                            
 
(0.2
)
Foreign currency translation                                                                                            
 
--
 
Asset retirement liability,  September 30, 2012
$
15.0