Annual report pursuant to Section 13 and 15(d)

Significant Accounting Policies - Percentage of Revenue by Major Customers (Details)

v3.10.0.1
Significant Accounting Policies - Percentage of Revenue by Major Customers (Details) - Sales Revenue Net - Customer Concentration Risk
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Shell Trading (US) Co.      
Entity Wide Revenue Major Customer [Line Items]      
Percentage of receipts 30.00% 46.00% 43.00%
BP Products North America      
Entity Wide Revenue Major Customer [Line Items]      
Percentage of receipts 20.00%    
Vitol Inc.      
Entity Wide Revenue Major Customer [Line Items]      
Percentage of receipts 14.00% 15.00% 20.00%