v3.3.0.814
Commitments and Contingencies - Additional Information (Detail) - USD ($)
$ in Millions
Sep. 30, 2015
Dec. 31, 2014
Commitments And Contingencies [Line Items]    
Accrued liabilities for remediation $ 1.1 $ 0.6
Maximum potential undiscounted payments 1.9  
Contractual commitments to acquire property, plant and equipment 49.6  
Environmental Loss Contingency [Member] | MPC [Member]    
Commitments And Contingencies [Line Items]    
Receivables from MPC for indemnification of environmental costs $ 0.1 $ 0.0