Net Sales by Geographic Region (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	May. 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May. 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May. 31, 2015	May. 31, 2014	May. 31, 2013
Segment Reporting Information [Line Items]
Net sales	$ 846,023	$ 804,785	$ 871,012	$ 862,414	$ 891,005	$ 773,230	$ 769,900	$ 692,291	$ 3,384,234	$ 3,126,426	$ 2,612,244
UNITED STATES
Segment Reporting Information [Line Items]
Net sales									3,175,972	2,917,484	2,418,307
Europe
Segment Reporting Information [Line Items]
Net sales									125,778	136,513	159,562
Mexico
Segment Reporting Information [Line Items]
Net sales									56,687	51,430
CANADA
Segment Reporting Information [Line Items]
Net sales									6,464	10,324	21,257
Other Countries
Segment Reporting Information [Line Items]
Net sales									$ 19,333	$ 10,675	$ 13,118