Stock-Based Compensation - Summary of Stock Option Activity under Company's Share-Based Compensation Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Oct. 31, 2012	Oct. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, beginning balance, weighted average exercise price	$ 29.24
Options outstanding, granted, weighted average exercise price	$ 30.21
Options outstanding, exercised, weighted average exercise price	$ 17.78
Options outstanding, forfeited or expired, weighted average exercise price	$ 30.49
Options outstanding, ending balance, weighted average exercise price	$ 29.56
Options outstanding, exercisable, weighted average exercise price	$ 29.78	$ 29.83
Options outstanding, ending balance, weighted average remaining contractual term	6 years 6 months
Options outstanding, exercisable, weighted average remaining contractual term	5 years
Options outstanding, ending balance, aggregate intrinsic value	$ 15,992
Options outstanding, exercisable, aggregate intrinsic value	$ 12,722
Options outstanding, beginning balance	6,253,751
Options outstanding, granted	760,350
Options outstanding, exercised	(167,636)
Options outstanding, forfeited or expired	(474,807)
Options outstanding, ending balance	6,371,658
Options outstanding, exercisable	4,231,429	3,975,963