Summary of Long-term Debt and Short-term Borrowings Outstanding (Parenthetical) (Detail)	12 Months Ended
	May 31, 2012 Floating rate senior notes due December 17, 2014	May 31, 2011 Floating rate senior notes due December 17, 2014	May 31, 2012 6.50% senior notes due April 15, 2020	May 31, 2011 6.50% senior notes due April 15, 2020	May 31, 2012 Industrial revenue bonds due March 2013	Dec. 29, 2011 Industrial revenue bonds due March 2013	May 31, 2012 Industrial revenue bonds due April 2019	Dec. 29, 2011 Industrial revenue bonds due April 2019
Debt Instrument [Line Items]
Debt, interest rate			6.50%	6.50%
Debt, maturity date	Dec. 17, 2014	Dec. 17, 2014	Apr. 15, 2020	Apr. 15, 2020
Debt, maturity date (year and month)					2013-03	2013-03	2019-04	2019-04