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Leases - Additional Information (Details) - USD ($)
$ in Millions
12 Months Ended
Sep. 01, 2016
Dec. 01, 2014
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Capital Leased Assets [Line Items]            
Rental expense     $ 0.2 $ 0.3 $ 0.5 $ 0.6
Short-term payment obligations     $ 8.3 $ 5.8    
Port Neches Tank Lease            
Capital Leased Assets [Line Items]            
Monthly lease payment $ 0.4          
Minimum actual and premises operating cost difference percentage required for lease adjustment (more than)   5.00%        
Imputed interest rate on capital portion of lease   15.00%