Entity Wide Disclosures - Geographic Breakdown of Revenues and Total Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014	May. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenues	$ 280,859	$ 240,619	$ 503,553	$ 428,740
Total Assets	819,868		819,868		$ 523,833
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenues	219,886	177,593	393,246	315,657
Total Assets	697,308		697,308		399,173
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenues	39,334	40,042	64,879	72,118
Total Assets	66,190		66,190		68,043
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenues	11,966	13,464	23,782	23,910
Total Assets	32,396		32,396		34,612
Other Foreign Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenues	9,673	$ 9,520	21,646	$ 17,055
Total Assets	$ 23,974		$ 23,974		$ 22,005