Annual report pursuant to Section 13 and 15(d)

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

v3.19.1
Commitments and Contingencies - Schedule of Letters of Credit (Details) - Letter of Credit - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Line of Credit Facility [Line Items]    
Total letters of credit $ 8,437 $ 6,523
Insurance programs    
Line of Credit Facility [Line Items]    
Total letters of credit 4,105 2,486
Environmental remediation    
Line of Credit Facility [Line Items]    
Total letters of credit 3,877 3,582
Rail car commitments    
Line of Credit Facility [Line Items]    
Total letters of credit $ 455 $ 455