Credit Facility (Details)		3 Months Ended
	Oct. 31, 2019 USD ($)	Oct. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)
Line of Credit Facility [Line Items]
New debt issuance maximum amount	$ 5,000,000	$ 5,000,000
Triggering event, days before maturity of old debt		91 days
Long-term line of credit	169,000,000	$ 169,000,000
Write-off of deferred financing costs		0	$ 3,217,000
Secured Credit Facility
Line of Credit Facility [Line Items]
Secured credit facility, maximum borrowing capacity	550,000,000	550,000,000
Outstanding standby letters of credit at period end	2,632,000	2,632,000
Outstanding commercial letters of credit at period end	0	0
Unamortized deferred financing costs	$ 2,943,000	2,943,000
Interest expense including amortization of deferred financing costs		$ 1,753,000	$ 2,542,000
Blended interest rate (percent)		4.70%	6.00%
Maximum amount of available cash on hand that can be used in leverage ratio calculation			$ 1,813,000
Leverage ratio	3.75
Maximum total leverage ratio	4.50
Fixed charge coverage ratio	3.25
Swingline Loan | Secured Credit Facility
Line of Credit Facility [Line Items]
Secured credit facility, maximum borrowing capacity	$ 25,000,000	$ 25,000,000
October 2018 Credit Facility [Member]
Line of Credit Facility [Line Items]
Minimum amount outstanding during period		142,000,000
Maximum amount outstanding during period		169,000,000
Revolving Loan Facility | Secured Credit Facility
Line of Credit Facility [Line Items]
Secured credit facility, maximum borrowing capacity	300,000,000	300,000,000
Line of credit facility, accordion feature	250,000,000	250,000,000
Letter of Credit | Secured Credit Facility
Line of Credit Facility [Line Items]
Secured credit facility, maximum borrowing capacity	$ 35,000,000	$ 35,000,000
Federal Funds Effective Swap 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%
Minimum | Secured Credit Facility
Line of Credit Facility [Line Items]
Interest expense coverage ratio	13.07
Maximum | Secured Credit Facility
Line of Credit Facility [Line Items]
Leverage ratio	1.75