Goodwill, Service Contracts and Other Assets (Information Regarding Service Contracts and Other Assets) (Details) (USD $) In Thousands, unless otherwise specified	May 31, 2014	May 31, 2013	May 31, 2012
Information regarding service contracts and other assets
Service contracts, Net	$ 55,675	$ 92,153	$ 76,822
Other assets, Carrying Amount	72,906	100,574
Other assets, Accumulated Amortization	53,280	77,709
Other assets, Net	19,626	22,865
Noncompete and consulting agreements [Member]
Information regarding service contracts and other assets
Other assets, Carrying Amount	49,080	77,863
Other assets, Accumulated Amortization	47,036	72,970
Other assets, Net	2,044	4,893
Other [Member]
Information regarding service contracts and other assets
Other assets, Carrying Amount	23,826	22,711
Other assets, Accumulated Amortization	6,244	4,739
Other assets, Net	17,582	17,972
Service contracts [Member]
Information regarding service contracts and other assets
Service contracts, Carrying Amount	360,634	420,499
Service contracts, Accumulated Amortization	304,959	328,346
Service contracts, Net	$ 55,675	$ 92,153