Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Aug. 31, 2016	May 31, 2018	May 31, 2017	May 31, 2016
Numerator (basic & diluted):
Net earnings attributable to controlling interest - income available to common shareholders	$ 30,770	$ 79,087	$ 39,403	$ 45,534	$ 56,494	$ 35,889	$ 46,565	$ 65,567	$ 194,794	$ 204,515	$ 143,715
Denominator:
Denominator for basic earnings per share attributable to controlling interest-weighted average common shares									60,923	62,443	62,469
Effect of dilutive securities									2,119	2,431	2,286
Denominator for diluted earnings per share attributable to controlling interest-adjusted weighted average common shares									63,042	64,874	64,755
Basic earnings per share attributable to controlling interest	$ 0.52	$ 1.31	$ 0.64	$ 0.73	$ 0.90	$ 0.57	$ 0.75	$ 1.06	$ 3.20	$ 3.28	$ 2.30
Diluted earnings per share attributable to controlling interest	$ 0.50	$ 1.27	$ 0.62	$ 0.70	$ 0.87	$ 0.55	$ 0.72	$ 1.02	$ 3.09	$ 3.15	$ 2.22