Commitments and Contingencies (Details) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Mar. 31, 2015
Legal Matters    
Estimated amount recoverable due to theft of fuel product $ 18.0  
Derailment of freight train    
Legal Matters    
Liabilities recorded based on estimated losses   42.2
Receivables for portion of liability recoverable from insurance   39.1
Derailment of freight train | Accrued expenses and other current liabilities    
Legal Matters    
Liabilities recorded based on estimated losses   16.3
Derailment of freight train | Other current assets    
Legal Matters    
Receivables for portion of liability recoverable from insurance   $ 29.4