Stock-Based Compensation - Summary of Activity under Company's Share-Based Compensation Plans (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jan. 31, 2015	Jan. 31, 2014
Summary of Stock Option Activity [Abstract]
Options Outstanding at July 31, 2014	4,204,260
Options Outstanding at July 31, 2014, Weighted Average Exercise Price	$ 30.82
Options, Grants in Period	618,733
Options, Grants in Period, Weighted Average Exercise Price	$ 22.70	$ 30.98
Options, Exercised in Period	(36,333)
Options, Exercised in Period, Weighted Average Exercise Price	$ 22.82
Options, Forfeitures and Expirations in Period	(1,048,929)
Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	$ 31.04
Options Outstanding at January 31, 2015	3,737,731
Options Outstanding at January 31, 2015, Weighted Average Exercise Price	$ 29.49
Options Outstanding, Exercisable	3,131,418	3,274,218
Options Outstanding, Exercisable, Weighted Average Exercise Price	$ 30.97	$ 31.14
Options Outstanding, Weighted Average Remaining Contractual Term	5 years 9 months 18 days
Options Outstanding, Aggregate Intrinsic Value	$ 3,108,904
Options Outstanding, Exercisable, Weighted Average Remaining Contractual Term	4 years 8 months 12 days
Options Outstanding, Exercisable, Aggregate Intrinsic Value	$ 1,005,722
Service Based Restricted Shares and Restricted Stock Units [Member]
Summary of Restricted Stock Unit and Restricted Share Activity [Abstract]
RSUs and Restricted Shares Outstanding at July 31, 2014	104,857
RSUs and Restricted Shares Outstanding at July 31, 2014, Weighted Average Grant Date Fair Value	$ 31.02
RSUs and Restricted Shares, Grants in Period	239,997
RSUs and Restricted Shares, Grants in Period, Weighted Average Grant Date Fair Value	$ 23.57
RSUs and Restricted Shares, Vested in Period	(34,247)
RSUs and Restricted Shares, Vested in Period, Weighted Average Grant Date Fair Value	$ 30.79
RSUs and Restricted Shares, Forfeited in Period	(24,641)
RSUs and Restricted Shares, Forfeitures, Weighted Average Grant Date Fair Value	$ 30.35
RSUs and Restricted Shares Outstanding at January 31, 2015	285,966
RSUs and Restricted Shares Outstanding at January 31, 2015, Weighted Average Grant Date Fair Value	$ 24.85
Performance Based Restricted Shares and Restricted Stock Units [Member]
Summary of Restricted Stock Unit and Restricted Share Activity [Abstract]
RSUs and Restricted Shares Outstanding at July 31, 2014	80,000
RSUs and Restricted Shares Outstanding at July 31, 2014, Weighted Average Grant Date Fair Value	$ 32.50
RSUs and Restricted Shares, Grants in Period	0
RSUs and Restricted Shares, Grants in Period, Weighted Average Grant Date Fair Value	$ 0.00
RSUs and Restricted Shares, Vested in Period	0
RSUs and Restricted Shares, Vested in Period, Weighted Average Grant Date Fair Value	$ 0.00
RSUs and Restricted Shares, Forfeited in Period	(80,000)
RSUs and Restricted Shares, Forfeitures, Weighted Average Grant Date Fair Value	$ 32.50
RSUs and Restricted Shares Outstanding at January 31, 2015	0
RSUs and Restricted Shares Outstanding at January 31, 2015, Weighted Average Grant Date Fair Value	$ 0.00