3% Convertible Senior Notes (Details) (USD $)	3 Months Ended	12 Months Ended
	Jul. 31, 2009	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Debt Disclosure [Abstract]
Debt instrument, face amount	$ 200,000,000
Net proceeds from debt issuance	194,541,000
Aggregate amount of initial purchasers' discount and other transaction costs related to debt issuance	5,459,000
Debt instrument, interest rate, stated percentage	3.00%
Amount of the 3.0% convertible senior notes converted into shares of common stock		50,037,000	0	0
Shares issued from the partial conversion of the 3.0% convertible senior notes (in shares)		1,570,904
Debt Instrument, convertible, conversion price		$ 31.85
Debt Instrument, convertible, conversion ratio		31.3953
Original principal amount of each 3.0% convertible senior note		1,000
Net increase to additional paid-in capital as a result of the partial conversion of the 3.0% convertible senior notes		49,596,000
Amount of the 3.0% convertible senior notes redeemed or repurchased for cash		149,963,000	0	0
Debt Instrument, Redemption Price, Percentage		100.00%
Amount of the 3.0% convertible senior notes outstanding at period end		$ 0	$ 200,000,000