Share-Based Compensation - Fair Value of Option Grant Estimated on Grant Date Using Black-Scholes Option-Pricing Model (Detail)	12 Months Ended
	Jul. 31, 2012		Jul. 31, 2011		Jul. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option term	5 years 9 months 18 days	[1]	6 years 1 month 6 days	[1]	5 years 2 months 12 days	[1]
Expected volatility factor	46.90%	[2]	44.50%	[2]	39.20%	[2]
Risk-free interest rate	1.30%	[3]	2.40%	[3]	2.20%	[3]
Expected annual dividend yield	0.00%	[4]	0.00%	[4]	0.00%	[4]

[1] Historical data on exercise patterns is the basis for estimating the expected life of an option.

[2] The stock volatility for each grant is measured using the weighted average of historical daily price changes of the Company's common stock over the most recent period equal to the expected option life of the grant, adjusted for activity which is not expected to occur in the future.

[3] The risk-free interest rate for periods equal to the expected term of the share option is based on the U.S. Treasury yield curve in effect at the time of grant.

[4] Excludes cash distributions that reduce additional paid in capital.