Computation of Basic and Diluted Earnings (Loss) per Share Attributable to Controlling Interest (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Numerator (basic & diluted):
Net earnings attributable to controlling interest - income available to common shareholders	$ 28,865	$ (25,710)	$ 29,462	$ 44,168	$ 33,163	$ 40,603	$ 22,977	$ 54,557	$ 76,785	$ 151,300	$ 136,442
Denominator:
Denominator for basic earnings per share attributable to controlling interest - weighted average common shares									66,309	68,944	69,301
Effect of dilutive securities									2,174	2,720	2,013
Denominator for diluted earnings per share attributable to controlling interest - adjusted weighted average common shares									68,483	71,664	71,314
Basic earnings per share attributable to controlling interest	$ 0.45	$ (0.39)	$ 0.44	$ 0.65	$ 0.49	$ 0.59	$ 0.33	$ 0.78	$ 1.16	$ 2.19	$ 1.97
Diluted earnings per share attributable to controlling interest	$ 0.44	$ (0.39)	$ 0.43	$ 0.63	$ 0.47	$ 0.57	$ 0.32	$ 0.76	$ 1.12	$ 2.11	$ 1.91