XML 59 R42.htm IDEA: XBRL DOCUMENT v3.8.0.1
Accounting for Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2017
Accounting for Asset Retirement Obligations [Abstract]  
Reconciliation of asset retirement obligations
The following is a reconciliation of asset retirement obligations as of December 31, 2017 and 2016:

 
 
2017
  
2016
 
 
 
(millions of dollars)
 
Asset retirement liability, beginning of period
 
$
21.5
  
$
21.4
 
Accretion expense
  
3.3
   
2.5
 
Payments
  
(3.2
)
  
(1.6
)
Foreign currency translation
  
0.5
   
(0.8
)
Asset retirement liability,  end of period
 
$
22.1
  
$
21.5