Summary of Unaudited Quarterly Consolidated Results of Operations (Detail) (USD $) In Thousands, except Per Share data, 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
Effect of Fourth Quarter Events [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
Gross margin	121,468	83,332	56,606	71,462	119,170	88,254	69,819	78,914	332,868	356,157	279,930
Net earnings attributable to controlling interest	$ 52,077	$ 25,880	$ 11,985	$ 25,653	$ 51,917	$ 26,326	$ 14,469	$ 22,354	$ 115,595	$ 115,066	$ 45,241
Earnings per share - basic	$ 0.76	$ 0.38	$ 0.17	$ 0.36	$ 0.71	$ 0.35	$ 0.20	$ 0.29	$ 1.66	$ 1.54	$ 0.57
Earnings per share - diluted	$ 0.75	$ 0.37	$ 0.17	$ 0.35	$ 0.70	$ 0.35	$ 0.20	$ 0.29	$ 1.65	$ 1.53	$ 0.57