Put and Call Option Contracts (Parenthetical) (Detail)	9 Months Ended
	Sep. 30, 2014
Minimum | Unleaded Fuel
Derivative [Line Items]
Derivative Settlement Month And Year	2014-10	[1]
Minimum | Diesel
Derivative [Line Items]
Derivative Settlement Month And Year	2014-10	[1]
Maximum | Unleaded Fuel
Derivative [Line Items]
Derivative Settlement Month And Year	2016-03	[1]
Maximum | Diesel
Derivative [Line Items]
Derivative Settlement Month And Year	2016-03	[1]

[1] The settlement of the put and call option contracts is based upon the New York Mercantile Exchange’s New York Harbor Reformulated Gasoline Blendstock for Oxygenate Blending and the U.S. Department of Energy’s weekly retail on-highway diesel fuel price for the month.