Secured Credit Facility (Details) - USD ($)	3 Months Ended	12 Months Ended
	Oct. 31, 2015	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014	Feb. 23, 2016	May 31, 2009
Line of Credit Facility [Line Items]
Outstanding standby letters of credit at period end		$ 4,650,000
Outstanding commercial letters of credit at period end		0
Stated interest rate						3.00%
Current portion of long-term debt		11,067,000	$ 0
Non-current portion of long-term debt, net		239,969,000	0
Secured Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity					$ 400,000,000
Repayments of Lines of Credit		97,352,000
Interest expense related to credit facility		$ 6,933,000
Debt, Weighted Average Interest Rate		5.00%
Long-term Debt		$ 251,036,000
Current portion of long-term debt		11,067,000
Non-current portion of long-term debt, net		239,969,000
Committed Secured Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000		100,000,000	$ 100,000,000
Line of credit facility, expiration date	Oct. 31, 2014
Interest expense related to credit facility			$ 198,000	673,000
3.0% Convertible Senior Notes [Member]
Line of Credit Facility [Line Items]
Interest expense related to convertible senior notes				$ 5,387,000
Stated interest rate						3.00%
Term Loan Facility [Member] | Secured Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt, Gross		172,647,000
Net deferred financing cost recorded as a direct deduction of non-current portion of debt		5,515,000
Line of credit facility, maximum borrowing capacity					250,000,000
Long-term Debt		167,132,000
Revolving Loan Facility [Member] | Secured Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity					150,000,000
Long-term Debt		$ 83,904,000
Revolving Loan Facility [Member] | Letter of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity					$ 25,000,000
Federal Funds Effective Swap Rate [Member] | Revolving Loan Facility [Member] | Secured Credit Facility
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.50%
Adjusted LIBO Rate [Member] | Revolving Loan Facility [Member] | Secured Credit Facility
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.00%