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Accounting for Asset Retirement Obligations (Tables)
 3 Months Ended
Mar. 31, 2013
Accounting for Asset Retirement Obligations [Abstract]  
Reconciliation of Asset Retirement Obligations
     The following is a reconciliation of asset retirement obligations as of March 31, 2013:

(millions of dollars)
 
 
 
 
 
 
 
Asset retirement liability, December 31, 2012
$
15.0
 
Accretion expense                                                                                            
 
0.2
 
Additions                                                                                            
 
0.1
 
Reversals                                                                                            
 
(0.3
)
Foreign currency translation and other                                                                                            
 
(0.1
)
Asset retirement liability,  March 31, 2013                                                                                            
$
14.9