Goodwill, Service Contracts and Other Assets Narrative (Details) (USD $)	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Goodwill, Service Contracts and Other Assets [Abstract]
Cash surrender value of insurance policies	$ 57,400,000	$ 51,100,000
Equity method investments	31,900,000	30,200,000
Cost method investments	900,000	2,900,000
Amortization expense	38,334,000	42,581,000	41,082,000
Estimated amortization expense, year one	21,800,000
Estimated amortization expense, year two	18,400,000
Estimated amortization expense, year three	15,500,000
Estimated amortization expense, year four	10,200,000
Estimated amortization expense, year five	$ 5,000,000