Goodwill, Service Contracts and Other Assets - Information Regarding Service Contracts and Other Assets (Details) - USD ($) $ in Thousands	Aug. 31, 2016	May 31, 2016
Information regarding service contracts and other assets
Service contracts, net	$ 84,792	$ 83,715
Other assets, carrying amount	58,899	57,653
Other assets, accumulated amortization	43,705	43,370
Other assets, net	15,194	14,283
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other assets, carrying amount	42,422	42,378
Other assets, accumulated amortization	41,045	40,928
Other assets, net	1,377	1,450
Other
Information regarding service contracts and other assets
Other assets, carrying amount	16,477	15,275
Other assets, accumulated amortization	2,660	2,442
Other assets, net	13,817	12,833
Service Contracts
Information regarding service contracts and other assets
Service contracts, carrying amount	399,738	395,482
Service contracts, accumulated amortization	314,946	311,767
Service contracts, net	$ 84,792	$ 83,715