Goodwill, Service Contracts and Other Assets - Information Regarding Service Contracts and Other Assets (Details) - USD ($) $ in Thousands	Aug. 31, 2017	May 31, 2017
Information regarding service contracts and other assets
Service contracts, net	$ 581,631	$ 586,988
Other assets, carrying amount	76,337	75,633
Other assets, accumulated amortization	45,710	43,666
Other assets, net	30,627	31,967
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other assets, carrying amount	40,918	40,743
Other assets, accumulated amortization	39,516	39,244
Other assets, net	1,402	1,499
Other
Information regarding service contracts and other assets
Other assets, carrying amount	35,419	34,890
Other assets, accumulated amortization	6,194	4,422
Other assets, net	29,225	30,468
Service Contracts
Information regarding service contracts and other assets
Service contracts, carrying amount	920,101	911,273
Service contracts, accumulated amortization	338,470	324,285
Service contracts, net	$ 581,631	$ 586,988