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Summary of Significant Accounting Policies - Conditional Asset Retirement Obligations (Details) - USD ($)
$ in Millions
1 Months Ended 12 Months Ended
Dec. 31, 2015
Dec. 31, 2016
Nov. 30, 2015
Nov. 30, 2014
Accounting Policies [Abstract]        
Useful life of property, plant and equipment, net   15 years    
Estimated retirement period of assets expected to be retired in 15 years   30 years    
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]        
Beginning Balance $ 29.3 $ 29.5 $ 24.4 $ 22.9
Additions and other, net   (0.9) 3.0 (0.2)
Accretion 0.2 2.0 1.9 1.7
Ending Balance $ 29.5 $ 30.6 $ 29.3 $ 24.4