Fuel Derivatives Outstanding (Detail)	6 Months Ended
	May 31, 2012 bbl
Fuel Derivatives 2012-Q3 & Q4 Maturity November 2011 Transaction Date
Derivative [Line Items]
Transaction Dates	2011-11	[1]
Barrels	1,044,000	[1]
Weighted-Average Floor Price	75	[1]
Weighted-Average Ceiling Price	135	[1]
Fuel Derivatives 2012-Q3 & Q4 Maturity February 2012 Transaction Date
Derivative [Line Items]
Transaction Dates	2012-02	[1]
Barrels	1,044,000	[1]
Weighted-Average Floor Price	109	[1]
Weighted-Average Ceiling Price	128	[1]
Fuel Derivatives 2012-Q3 & Q4 Maturity March 2012 Transaction Date
Derivative [Line Items]
Transaction Dates	2012-03	[1]
Barrels	2,088,000	[1]
Weighted-Average Floor Price	112	[1]
Weighted-Average Ceiling Price	132	[1]
Fuel Derivatives 2012-Q3 & Q4 Maturity
Derivative [Line Items]
Barrels	4,176,000	[1]
Percent of Estimated Fuel Consumption	38.00%	[1]
Fuel Derivatives 2013 Maturity November 2011 Transaction Date
Derivative [Line Items]
Transaction Dates	2011-11	[1]
Barrels	2,112,000	[1]
Weighted-Average Floor Price	74	[1]
Weighted-Average Ceiling Price	132	[1]
Fuel Derivatives 2013 Maturity February 2012 Transaction Date
Derivative [Line Items]
Transaction Dates	2012-02	[1]
Barrels	2,112,000	[1]
Weighted-Average Floor Price	98	[1]
Weighted-Average Ceiling Price	127	[1]
Fuel Derivatives 2013 Maturity March 2012 Transaction Date
Derivative [Line Items]
Transaction Dates	2012-03	[1]
Barrels	4,224,000	[1]
Weighted-Average Floor Price	100	[1]
Weighted-Average Ceiling Price	130	[1]
Fuel Derivatives 2013 Maturity
Derivative [Line Items]
Barrels	8,448,000	[1]
Percent of Estimated Fuel Consumption	38.00%	[1]
Fuel Derivatives 2014 Maturity November 2011 Transaction Date
Derivative [Line Items]
Transaction Dates	2011-11	[1]
Barrels	2,112,000	[1]
Weighted-Average Floor Price	71	[1]
Weighted-Average Ceiling Price	128	[1]
Fuel Derivatives 2014 Maturity February 2012 Transaction Date
Derivative [Line Items]
Transaction Dates	2012-02	[1]
Barrels	2,112,000	[1]
Weighted-Average Floor Price	88	[1]
Weighted-Average Ceiling Price	125	[1]
Fuel Derivatives 2014 Maturity
Derivative [Line Items]
Barrels	4,224,000	[1]
Percent of Estimated Fuel Consumption	19.00%	[1]
Fuel Derivatives 2015 Maturity November 2011 Transaction Date
Derivative [Line Items]
Transaction Dates	2011-11	[1]
Barrels	2,160,000	[1]
Weighted-Average Floor Price	71	[1]
Weighted-Average Ceiling Price	125	[1]
Fuel Derivatives 2015 Maturity February 2012 Transaction Date
Derivative [Line Items]
Transaction Dates	2012-02	[1]
Barrels	2,160,000	[1]
Weighted-Average Floor Price	80	[1]
Weighted-Average Ceiling Price	125	[1]
Fuel Derivatives 2015 Maturity
Derivative [Line Items]
Barrels	4,320,000	[1]
Percent of Estimated Fuel Consumption	19.00%	[1]

[1] Fuel derivatives mature evenly over each month within the above fiscal periods.