SCHEDULE II - Valuation and Qualifying Accounts (Detail) (Allowance for Doubtful Accounts, USD $)	12 Months Ended
	May 31, 2014		May 31, 2013		May 31, 2012
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 3,408,000		$ 3,329,000		$ 4,150,000
Charged to Costs and Expenses	32,000		783,000		339,000
Charged to Other Accounts - Describe			26,000	[1]	370,000	[1]
Deductions - Describe	397,000	[2]	730,000	[2]	1,530,000	[2]
Balance at End of Period	$ 3,043,000		$ 3,408,000		$ 3,329,000

[1] Miscellaneous amounts.

[2] Uncollectable accounts charged to the allowance.