Stock Option and Restricted Stock Awards Transactions (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Jul. 31, 2012		Jul. 31, 2011
Outstanding Stock Awards
Number of Shares
Outstanding at beginning period	274,522
Granted	132,333
Exercised	(35,922)
Cancelled (forfeited and expired)	(29,439)
Outstanding at end period	341,494		274,522
Options vested or expected to vest at end period	329,147	[1]
Options exercisable at end period	198,984
Weighted Average Exercise Price
Outstanding at beginning period	$ 55.18
Granted	$ 47.09
Exercised	$ 46.79
Cancelled (forfeited and expired)	$ 46.59
Outstanding at end period	$ 53.67		$ 55.18
Options vested or expected to vest at end period	$ 53.92	[1]
Options exercisable at end period	$ 58.61
Weighted Average Remaining Contractual Term (Years)
Outstanding at end period	4 years 6 months 26 days		4 years 4 months 2 days
Options vested or expected to vest at end period	4 years 6 months 11 days	[1]
Options exercisable at end period	3 years 4 months 10 days
Aggregate Intrinsic Value
Outstanding at beginning period	$ 1,466
Outstanding at end period	3,708		1,466
Options vested or expected to vest at end period	3,576	[1]
Options exercisable at end period	$ 1,315
Time Based Restricted Stock
Number of Shares/Units
Outstanding at beginning period	51,800
Granted	109,338
Vesting of restricted stock	(29,811)
Cancelled (forfeited and expired)	(8,256)
Outstanding at end period	123,071
Weighted Average Grant Date Fair Value
Outstanding at beginning period	$ 44.90
Granted	$ 51.11
Exercised
Vesting of restricted stock	$ 53.59
Cancelled (forfeited and expired)	$ 43.66
Outstanding at end period	$ 48.40
Performance awards
Number of Shares/Units
Outstanding at beginning period	447,244	[2]
Granted	76,084	[2]
Vesting of restricted stock	(9,665)	[2]
Cancelled (forfeited and expired)	(62,213)	[2]
Outstanding at end period	451,450	[2]
Weighted Average Grant Date Fair Value
Outstanding at beginning period	$ 46.95
Granted	$ 77.54
Exercised
Vesting of restricted stock	$ 45.98
Cancelled (forfeited and expired)	$ 45.87
Outstanding at end period	$ 52.29

[1] In addition to the vested options, the Company expects a portion of the unvested options to vest at some point in the future. Options expected to vest are calculated by applying an estimated forfeiture rate to the unvested options.

[2] The number of performance-based unvested restricted stock awards is shown in this table at target. As of July 31, 2012, the maximum number of performance-based unvested restricted stock awards available to be earned is 902,900.