Long-Term Debt (Parenthetical) (Detail)	Feb. 29, 2012	Nov. 30, 2011	Jan. 31, 2011
5.4 percent Senior Notes
Debt Instrument [Line Items]
Debt, interest rate	5.40%	5.40%
4.6 percent Senior Notes
Debt Instrument [Line Items]
Debt, interest rate	4.60%	4.60%	4.60%
4.8 percent Revenue Bonds
Debt Instrument [Line Items]
Debt, interest rate	4.80%	4.80%
6.3 percent Term Loan
Debt Instrument [Line Items]
Debt, interest rate	6.30%	6.30%