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Accounting for Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2019
Accounting for Asset Retirement Obligations [Abstract]  
Reconciliation of Asset Retirement Obligations

The following is a reconciliation of asset retirement obligations as of December 31, 2019 and 2018:


  
December 31,
  
(millions of dollars)
  
2019
    
2018
  
Asset retirement liability, beginning of period
  
$
23.4
    
$
22.1
  
Accretion expense
    
2.7
      
1.0
  
Other
    
1.1
      
2.1
  
Payments
    
(3.3
)
    
(1.3
)
Foreign currency translation
    
—
      
(0.5
)
Asset retirement liability, end of period
  
$
23.9
    
$
23.4