Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	May 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2014	May 31, 2013	May 31, 2012
Numerator (basic & diluted):
Net earnings attributable to controlling interest - income available to common shareholders	$ 33,163	$ 40,603	$ 22,977	$ 54,557	$ 33,523	$ 37,131	$ 31,826	$ 33,962	$ 151,300	$ 136,442	$ 115,595
Denominator:
Denominator for basic earnings per share attributable to controlling interest - weighted average common shares									68,944	69,301	69,651
Effect of dilutive securities									2,720	2,013	601
Denominator for diluted earnings per share attributable to controlling interest - adjusted weighted average common shares									71,664	71,314	70,252
Basic earnings per share attributable to controlling interest	$ 0.49	$ 0.59	$ 0.33	$ 0.78	$ 0.48	$ 0.53	$ 0.46	$ 0.50	$ 2.19	$ 1.97	$ 1.66
Diluted earnings per share attributable to controlling interest	$ 0.47	$ 0.57	$ 0.32	$ 0.76	$ 0.46	$ 0.52	$ 0.45	$ 0.49	$ 2.11	$ 1.91	$ 1.65