Goodwill, Service Contracts and Other Assets - Information Regarding Service Contracts and Other Assets (Details) - USD ($) $ in Thousands	Aug. 31, 2015	May. 31, 2015
Information regarding service contracts and other assets
Service contracts, net	$ 75,306	$ 42,434
Other assets, carrying amount	69,303	65,423
Other assets, accumulated amortization	48,395	47,929
Other assets, net	20,908	17,494
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other assets, carrying amount	42,290	41,828
Other assets, accumulated amortization	40,483	40,379
Other assets, net	1,807	1,449
Other
Information regarding service contracts and other assets
Other assets, carrying amount	27,013	23,595
Other assets, accumulated amortization	7,912	7,550
Other assets, net	19,101	16,045
Service Contracts
Information regarding service contracts and other assets
Service contracts, carrying amount	375,647	340,816
Service contracts, accumulated amortization	300,341	298,382
Service contracts, net	$ 75,306	$ 42,434