Derivatives - Open Commodity Derivative Contracts - Refined Products (Detail) - Refined products - Exchange Traded
gal in Thousands
3 Months Ended
Mar. 31, 2018
gal
Derivative [Line Items]  
Percentage of derivative contracts expiring in the period 100.00%
Derivative contract expiration date Jun. 30, 2017
Long  
Derivative [Line Items]  
Notional contracts (in thousands of Total Gallons) 159,390 [1]
Short  
Derivative [Line Items]  
Notional contracts (in thousands of Total Gallons) 147,252 [1]
[1] of the exchange-traded contracts expire in the second quarter of 2018.