Goodwill, Service Contracts and Other Assets - Information Regarding Service Contracts and Other Assets (Details) - USD ($) $ in Thousands	May 31, 2017	May 31, 2016	May 31, 2015
Information regarding service contracts and other assets
Service contracts, net	$ 586,988	$ 78,194	$ 35,650
Other assets, carrying amount	75,633	55,513
Other assets, accumulated amortization	43,666	41,230
Other assets, net	31,967	14,283
Noncompete and consulting agreements
Information regarding service contracts and other assets
Other assets, carrying amount	40,743	40,238
Other assets, accumulated amortization	39,244	38,788
Other assets, net	1,499	1,450
Other
Information regarding service contracts and other assets
Other assets, carrying amount	34,890	15,275
Other assets, accumulated amortization	4,422	2,442
Other assets, net	30,468	12,833
Service contracts
Information regarding service contracts and other assets
Service contracts, carrying amount	911,273	382,858
Service contracts, accumulated amortization	324,285	304,664
Service contracts, net	$ 586,988	$ 78,194