Earnings (Loss) Per Share (Detail) - Schedule of Calculation of Numerator and Denominator in Earnings Per Share (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011	Nov. 30, 2010
Earnings from continuing operations attributable to Class A and Common Shares (in Dollars)	$ 82.9	$ 76.8	$ 57.9	$ 43.0
Loss from discontinued operations attributable to Class A and Common Shares, net of tax (in Dollars)	(0.5)	(2.2)	(2.5)	(3.5)
Net income attributable to Class A and Common Shares (in Dollars)	$ 82.4	$ 74.6	$ 55.4	$ 39.5
Weighted average Shares of Class A Stock and Common Stock outstanding for basic earnings per share (in millions) (in Shares)	31.2	34.4	31.1	35.3
Dilutive effect of Class A Stock and Common Stock potentially issuable pursuant to stock-based compensation plans (in millions) (in Shares)	0.5	0.5	0.5	0.4
Adjusted weighted average Shares of Class A Stock and Common Stock outstanding for diluted earnings per share (in millions) (in Shares)	31.7	34.9	31.6	35.7
Basic earnings (loss) per share:
Earnings from continuing operations	$ 2.66	$ 2.23	$ 1.86	$ 1.22
Loss from discontinued operations, net of tax	$ (0.02)	$ (0.06)	$ (0.08)	$ (0.10)
Net income	$ 2.64	$ 2.17	$ 1.78	$ 1.12
Diluted earnings (loss) per share:
Earnings from continuing operations	$ 2.62	$ 2.20	$ 1.83	$ 1.21
Loss from discontinued operations, net of tax	$ (0.02)	$ (0.06)	$ (0.08)	$ (0.10)
Net income	$ 2.60	$ 2.14	$ 1.75	$ 1.11