Earnings (Loss) Per Share (Detail) - Summary of reconciliation of the numerators and denominators for the Basic and Diluted earnings (loss) per share (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2012	Nov. 30, 2011
Earnings (loss) from continuing operations attributable to Class A and Common Shares (in Dollars)	$ 61.7	$ 82.9	$ 29.8	$ 57.9
Earnings (loss) from discontinued operations attributable to Class A and Common Shares, net of tax (in Dollars)	(0.1)	(0.5)	(0.2)	(2.5)
Net income (loss) attributable to Class A and Common Shares (in Dollars)	$ 61.6	$ 82.4	$ 29.6	$ 55.4
Weighted average Shares of Class A Stock and Common Stock outstanding for basic earnings (loss) per share (in millions) (in Shares)	31.9	31.2	31.7	31.1
Dilutive effect of Class A Stock and Common Stock potentially issuable pursuant to stock-based compensation plans (in millions) (in Shares)	0.8	0.5	0.7	0.5
Adjusted weighted average Shares of Class A Stock and Common Stock outstanding for diluted earnings (loss) per share (in millions) (in Shares)	32.7	31.7	32.4	31.6
Basic earnings (loss) per share:
Earnings (loss) from continuing operations	$ 1.93	$ 2.66	$ 0.94	$ 1.86
Earnings (loss) from discontinued operations, net of tax	$ 0.00	$ (0.02)	$ (0.01)	$ (0.08)
Net income (loss)	$ 1.93	$ 2.64	$ 0.93	$ 1.78
Diluted earnings (loss) per share:
Earnings (loss) from continuing operations	$ 1.89	$ 2.62	$ 0.92	$ 1.83
Earnings (loss) from discontinued operations, net of tax	$ 0.00	$ (0.02)	$ (0.01)	$ (0.08)
Net income (loss)	$ 1.89	$ 2.60	$ 0.91	$ 1.75