Goodwill, Service Contracts and Other Assets - Information Regarding Service Contracts and Other Assets (Details) - USD ($) $ in Thousands	Feb. 28, 2017	May 31, 2016
Information regarding service contracts and other assets
Service contracts, net	$ 83,720	$ 83,715
Other assets, carrying amount	60,567	57,653
Other assets, accumulated amortization	44,479	43,370
Other assets, net	16,088	14,283
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other assets, carrying amount	42,822	42,378
Other assets, accumulated amortization	41,278	40,928
Other assets, net	1,544	1,450
Other
Information regarding service contracts and other assets
Other assets, carrying amount	17,745	15,275
Other assets, accumulated amortization	3,201	2,442
Other assets, net	14,544	12,833
Service Contracts
Information regarding service contracts and other assets
Service contracts, carrying amount	404,894	395,482
Service contracts, accumulated amortization	321,174	311,767
Service contracts, net	$ 83,720	$ 83,715