Goodwill, Service Contracts and Other Assets - Information Regarding Service Contracts and Other Assets (Details) - USD ($) $ in Thousands	Feb. 29, 2016	May. 31, 2015
Information regarding service contracts and other assets
Service contracts, net	$ 86,380	$ 42,434
Other assets, carrying amount	68,042	65,423
Other assets, accumulated amortization	49,757	47,929
Other assets, net	18,285	17,494
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other assets, carrying amount	42,321	41,828
Other assets, accumulated amortization	40,754	40,379
Other assets, net	1,567	1,449
Other
Information regarding service contracts and other assets
Other assets, carrying amount	25,721	23,595
Other assets, accumulated amortization	9,003	7,550
Other assets, net	16,718	16,045
Service Contracts
Information regarding service contracts and other assets
Service contracts, carrying amount	394,326	340,816
Service contracts, accumulated amortization	307,946	298,382
Service contracts, net	$ 86,380	$ 42,434