Goodwill, Service Contracts and Other Assets - Information Regarding Service Contracts and Other Assets (Details) - USD ($) $ in Thousands	Feb. 28, 2018	May 31, 2017
Information regarding service contracts and other assets
Service contracts, net	$ 557,477	$ 586,988
Other assets, carrying amount	74,920	75,633
Other assets, accumulated amortization	49,354	43,666
Other assets, net	25,566	31,967
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other assets, carrying amount	41,358	40,743
Other assets, accumulated amortization	39,740	39,244
Other assets, net	1,618	1,499
Other
Information regarding service contracts and other assets
Other assets, carrying amount	33,562	34,890
Other assets, accumulated amortization	9,614	4,422
Other assets, net	23,948	30,468
Service Contracts
Information regarding service contracts and other assets
Service contracts, carrying amount	923,020	911,273
Service contracts, accumulated amortization	365,543	324,285
Service contracts, net	$ 557,477	$ 586,988