Goodwill, Service Contracts and Other Assets - Information Regarding Service Contracts and Other Assets (Details) - USD ($) $ in Thousands	May 31, 2018	May 31, 2017	May 31, 2016
Information regarding service contracts and other assets
Service contracts, net	$ 545,768	$ 586,988	$ 78,194
Other assets, carrying amount	80,497	75,633
Other assets, accumulated amortization	51,182	43,666
Other assets, net	29,315	31,967
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other assets, carrying amount	41,710	40,743
Other assets, accumulated amortization	39,877	39,244
Other assets, net	1,833	1,499
Other
Information regarding service contracts and other assets
Other assets, carrying amount	38,787	34,890
Other assets, accumulated amortization	11,305	4,422
Other assets, net	27,482	30,468
Service contracts
Information regarding service contracts and other assets
Service contracts, carrying amount	924,978	911,273
Service contracts, accumulated amortization	379,210	324,285
Service contracts, net	$ 545,768	$ 586,988