Goodwill, Service Contracts and Other Assets (Details 3) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2012		May 31, 2012
Information regarding service contracts and other assets
Service contracts, Net	$ 72,297		$ 76,822
Other Assets, Carrying Amount	188,025		186,062
Other Assets, Accumulated Amortization	74,829		73,226
Other Assets, Net	113,196		112,836
Noncompete agreements [Member]
Information regarding service contracts and other assets
Other Assets, Carrying Amount	76,279		76,036
Other Assets, Accumulated Amortization	71,177		69,954
Other Assets, Net	5,102		6,082
Investments [Member]
Information regarding service contracts and other assets
Other Assets, Carrying Amount	91,723	[1]	90,198	[1]
Other Assets, Accumulated Amortization	0	[1]	0	[1]
Other Assets, Net	91,723	[1]	90,198	[1]
Other [Member]
Information regarding service contracts and other assets
Other Assets, Carrying Amount	20,023		19,828
Other Assets, Accumulated Amortization	3,652		3,272
Other Assets, Net	16,371		16,556
Service Contracts [Member]
Information regarding service contracts and other assets
Service contracts, Carrying Amount	386,144		384,622
Service contracts, Accumulated Amortization	313,847		307,800
Service contracts, Net	$ 72,297		$ 76,822

[1] Investments at August 31, 2012, include the cash surrender value of insurance policies of $59.3 million, equity method investments of $31.5 million and cost method investments of $0.9 million. Investments at May 31, 2012, include the cash surrender value of insurance policies of $57.4 million, equity method investments of $31.9 million and cost method investments of $0.9 million.