Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Schedule of Letters of Credit (Details)

v3.10.0.1
Commitments and Contingencies - Schedule of Letters of Credit (Details) - Letter of Credit - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Line of Credit Facility [Line Items]    
Total letters of credit $ 6,523 $ 6,523
Environmental remediation    
Line of Credit Facility [Line Items]    
Total letters of credit 3,582 3,582
Insurance programs    
Line of Credit Facility [Line Items]    
Total letters of credit 2,486 2,486
Rail car commitments    
Line of Credit Facility [Line Items]    
Total letters of credit $ 455 $ 455