Goodwill, Service Contracts and Other Assets (Details 3) (USD $)	3 Months Ended
	Aug. 31, 2011	Aug. 31, 2010	May 31, 2011
Information regarding service contracts and other assets
Other Assets, Carrying Amount	$ 187,318,000		$ 183,423,000
Other Assets, Accumulated Amortization	71,090,000		68,672,000
Other Assets, Net	116,228,000		114,751,000
Investments
Cash surrender value of insurance policies	54,100,000		51,100,000
Equity method investments	30,900,000		30,200,000
Cost method investments	2,900,000		2,900,000
Amortization
Amortization expense	10,233,000	10,429,000
Estimated amortization expense, year one	38,000,000
Estimated amortization expense, year two	21,000,000
Estimated amortization expense, year three	17,500,000
Estimated amortization expense, year four	14,700,000
Estimated amortization expense, year five	9,500,000
Service Contracts
Information regarding service contracts and other assets
Service contracts, Carrying Amount	380,302,000		379,967,000
Service contracts, Accumulated Amortization	285,871,000		277,655,000
Service contracts, Net	94,431,000		102,312,000
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other Assets, Carrying Amount	76,387,000		76,091,000
Other Assets, Accumulated Amortization	65,982,000		63,982,000
Other Assets, Net	10,405,000		12,109,000
Investments
Information regarding service contracts and other assets
Other Assets, Carrying Amount	87,924,000		84,197,000
Other Assets, Net	87,924,000		84,197,000
Other
Information regarding service contracts and other assets
Other Assets, Carrying Amount	23,007,000		23,135,000
Other Assets, Accumulated Amortization	5,108,000		4,690,000
Other Assets, Net	$ 17,899,000		$ 18,445,000