Secured Credit Facility (Details)		3 Months Ended
	Oct. 31, 2017 USD ($) $ / shares	Oct. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)	Jul. 31, 2017 USD ($)	Feb. 23, 2016 USD ($)
Line of Credit Facility [Line Items]
Current portion of long-term debt	$ 16,135,000	$ 16,135,000		$ 15,494,000
Non-current portion of long-term debt, net	175,193,000	175,193,000		176,228,000
Repayment of term loan facility		7,127,000	$ 2,212,000
Secured Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt	191,328,000	191,328,000		191,722,000
Current portion of long-term debt	16,135,000	16,135,000		15,494,000
Non-current portion of long-term debt, net	$ 175,193,000	175,193,000		176,228,000
Secured credit facility, maximum borrowing capacity					$ 400,000,000
Interest expense including amortization of deferred financing costs		$ 2,465,000	$ 3,175,000
Blended interest rate (percent)	5.30%	5.30%	5.00%
Outstanding standby letters of credit at period end	$ 3,013,000	$ 3,013,000
Outstanding commercial letters of credit at period end	0	0
Maximum amount of available cash on hand that can be used in leverage ratio calculation	$ 50,000,000	50,000,000
Leverage ratio	2.83
Fixed charge coverage ratio	2.03
Targeted quarterly dividend per share | $ / shares	$ 0.10
Term Loan Facility | Secured Credit Facility
Line of Credit Facility [Line Items]
Long-term debt, gross	$ 131,953,000	131,953,000		139,080,000
Unamortized deferred financing costs	4,430,000	4,430,000		4,763,000
Long-term Debt	127,523,000	127,523,000		134,317,000
Secured credit facility, maximum borrowing capacity					250,000,000
Repayment of term loan facility		7,127,000	$ 2,212,000
Revolving Loan Facility | Secured Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt	$ 63,805,000	$ 63,805,000		$ 57,405,000
Secured credit facility, maximum borrowing capacity					150,000,000
Revolving Loan Facility | Letter of Credit
Line of Credit Facility [Line Items]
Secured credit facility, maximum borrowing capacity					$ 25,000,000
Federal Funds Effective Rate | Revolving Loan Facility | Secured Credit Facility
Line of Credit Facility [Line Items]
Variable interest rate (percent)		0.50%
Adjusted LIBO rate | Revolving Loan Facility | Secured Credit Facility
Line of Credit Facility [Line Items]
Variable interest rate (percent)		1.00%
Floor interest rate		1.00%
Minimum | Secured Credit Facility
Line of Credit Facility [Line Items]
Fixed charge coverage ratio	1.25
Minimum | Revolving Loan Facility | Secured Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt	$ 41,904,000	$ 41,904,000
Maximum | Secured Credit Facility
Line of Credit Facility [Line Items]
Leverage ratio	3.50
Maximum | Revolving Loan Facility | Secured Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt	$ 63,804,000	63,804,000
Fourth quarter of fiscal 2018 and thereafter | Maximum | Secured Credit Facility
Line of Credit Facility [Line Items]
Leverage ratio	3.00
Due by February 23, 2021 | Term Loan Facility | Secured Credit Facility
Line of Credit Facility [Line Items]
Balloon payment to be made	$ 22,500,000	$ 22,500,000