Derivatives - Open Commodity Derivative Contracts (Detail)	9 Months Ended
	Sep. 30, 2014
Crude Oil Exchange-Traded
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	96.00%
Derivative contract expiration date	Dec. 31, 2014
Crude Oil Exchange-Traded | Long
Derivative [Line Items]
Notional Contracts (in thousands of Total Barrels)	10,346,000	[1]
Crude Oil Exchange-Traded | Short
Derivative [Line Items]
Notional Contracts (in thousands of Total Barrels)	23,186,000	[1]
Refined Products Exchange-Traded
Derivative [Line Items]
Percentage of derivative contracts expiring in the period	100.00%
Derivative contract expiration date	Dec. 31, 2014
Refined Products Exchange-Traded | Long
Derivative [Line Items]
Notional Contracts (in thousands of Total Barrels)	1,695,000	[2]
Refined Products Exchange-Traded | Short
Derivative [Line Items]
Notional Contracts (in thousands of Total Barrels)	3,281,000	[2]

[1] 96 percent of these contracts expire in the fourth quarter of 2014.

[2] 100 percent of these contracts expire in the fourth quarter of 2014.