Annual report pursuant to Section 13 and 15(d)

Related Parties - Additional Information (Details)

v3.8.0.1
Related Parties - Additional Information (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Related Party Transaction [Line Items]      
Principal $ 889,790 $ 873,733  
Airplane Services      
Related Party Transaction [Line Items]      
Related party transactions 1,200 1,100 $ 1,100
Marine Transportation and Logistic Services      
Related Party Transaction [Line Items]      
Related party transactions 200    
Payments to related party transactions $ 22,800    
Marine Transportation and Logistic Services | Maximum      
Related Party Transaction [Line Items]      
Related party transactions   $ 200 200
CEO and Largest Shareholder | Second Lien Term Loan      
Related Party Transaction [Line Items]      
Principal     $ 5,000