Stock-Based Compensation (Details1) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jan. 31, 2012 Y	Jan. 31, 2011
Summary of stock option activity under the Company's share-based compensation plans
Options outstanding, beginning balance	5,726,017
Options outstanding, granted	1,206,150
Options outstanding, exercised	(104,119)
Options outstanding, forfeited or expired	(154,199)
Options outstanding, ending balance	6,673,849
Options outstanding, exercisable	4,024,955	3,499,632
Options outstanding, beginning balance, weighted average exercise price	$ 29.24
Options outstanding, granted, weighted average exercise price	$ 27.88
Options outstanding, exercised, weighted average exercise price	$ 22.10
Options outstanding, forfeited or expired, weighted average exercise price	$ 33.76
Options outstanding, ending balance, weighted average exercise price	$ 29.00
Options outstanding, exercisable, weighted average exercise price	$ 29.31	$ 29.28
Options outstanding, ending balance, weighted average remaining contractual term	6.6
Options outstanding, exercisable, weighted average remaining contractual term	5.2
Options outstanding, ending balance, aggregate intrinsic value	$ 18,318
Options outstanding, exercisable, aggregate intrinsic value	$ 14,018