Goodwill, Service Contracts and Other Assets (Information Regarding Service Contracts and Other Assets) (Details) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2014	May 31, 2014
Information regarding service contracts and other assets
Service contracts, Net	$ 44,185	$ 55,675
Other Assets, Carrying Amount	65,266	72,906
Other Assets, Accumulated Amortization	46,488	53,280
Other Assets, Net	18,778	19,626
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other Assets, Carrying Amount	41,261	49,080
Other Assets, Accumulated Amortization	39,882	47,036
Other Assets, Net	1,379	2,044
Other
Information regarding service contracts and other assets
Other Assets, Carrying Amount	24,005	23,826
Other Assets, Accumulated Amortization	6,606	6,244
Other Assets, Net	17,399	17,582
Service Contracts
Information regarding service contracts and other assets
Service contracts, Carrying Amount	336,083	360,634
Service contracts, Accumulated Amortization	291,898	304,959
Service contracts, Net	$ 44,185	$ 55,675