Net Sales by Geographic Region (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2011	Feb. 28, 2011	Nov. 30, 2010	Aug. 31, 2010	May 31, 2012	May 31, 2011	May 31, 2010
Segment Reporting Information [Line Items]
Net sales	$ 755,407	$ 611,255	$ 565,652	$ 602,387	$ 675,693	$ 569,439	$ 580,687	$ 616,805	$ 2,534,701	$ 2,442,624	$ 1,943,034
UNITED STATES
Segment Reporting Information [Line Items]
Net sales									2,333,575	2,256,579	1,832,286
CANADA
Segment Reporting Information [Line Items]
Net sales									29,097	32,891	39,751
Europe
Segment Reporting Information [Line Items]
Net sales									150,458	116,071	70,997
Other Countries
Segment Reporting Information [Line Items]
Net sales									$ 21,571	$ 37,083