XML 57 R42.htm IDEA: XBRL DOCUMENT v3.8.0.1
Asset Retirement Obligations (Details) - USD ($)
$ in Millions
9 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Divestitures [Line Items]    
Asset Retirement Obligation, Current $ 4.9 $ 5.8
ARO Liability [Roll Forward]    
ARO liability, Beginning Balance 231.6  
Accretion 6.0  
Additions 6.2  
Revisions 0.2  
Liabilities related to assets sold [1] (40.8)  
Liabilities settled (9.0)  
ARO liability, Ending Balance 194.2  
Pinedale Divestiture [Member]    
ARO Liability [Roll Forward]    
Liabilities related to assets sold $ 34.9  
[1] Liabilities related to assets sold for the nine months ended September 30, 2017, includes $34.9 million related to the Pinedale Divestiture (refer to Note 2 – Acquisitions and Divestitures for more information).