Valuation and Qualifying Accounts (Detail) (Allowance for Doubtful Accounts, USD $)	12 Months Ended
	May 31, 2012		May 31, 2011		May 31, 2010
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 4,150,000		$ 5,752,000		$ 12,470,000
Charged to Costs and Expenses	339,000		1,236,000		(900,000)	[1]
Charged to Other Accounts - Describe	370,000	[2]	106,000	[2]	29,000	[2]
Deductions - Describe	1,530,000	[3]	2,732,000	[3],[4]	5,847,000	[3]
Balance at End of Period	$ 3,329,000		$ 4,150,000		$ 5,752,000

[1] Net allowance reversal, adjusted through expense.

[2] Miscellaneous amounts.

[3] Uncollectable accounts charged to the allowance.

[4] Includes $686,000 related to the deconsolidation of our metal framing business.