Long-Term Debt (Details Textuals) - USD ($) $ in Thousands		4 Months Ended	12 Months Ended			15 Months Ended	20 Months Ended
	Jul. 21, 2016	Jul. 21, 2016	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015	Mar. 14, 2016	Jul. 21, 2016	Mar. 15, 2016	Dec. 03, 2014
Line of Credit Facility [Line Items]
Total Consolidated Net Leverage Ratio			83.00%
Minimum Liquidity			$ 803,200
Applicable interest rate added to reference rate in order to compute variable interest rate			1.00%
Reference rate			1.23%
Debt instrument costs			$ 0	$ 1,179	$ 955
Amortization of Debt Issuance Costs				600
Federal Funds Rate
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate			0.50%
LIBOR
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate			1.00%
Adjusted LIBOR One | Minimum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate		0.125%
Adjusted LIBOR One | Maximum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate		1.00%
Adjusted LIBOR Two | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate		1.125%
Line of Credit | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Commitment fee rate range		0.15%
Line of Credit | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Commitment fee rate range		0.30%
Scenario 1 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Covenant Terms 1			325.00%
Note Agreement, Covenant Terms			325.00%
Scenario 2 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Covenant Terms 1			350.00%
Note Agreement, Covenant Terms			350.00%
Wells Fargo and Bank of America
Line of Credit Facility [Line Items]
Maturity date		Mar. 15, 2021
Wells Fargo and Bank of America | Adjusted LIBOR Two | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate		2.00%
Wells Fargo and Bank of America | Line of Credit
Line of Credit Facility [Line Items]
Repayments of lines of credit	$ 242,500
Wells Fargo and Bank of America | Line of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity									$ 300,000
Outstanding borrowings			$ 0
Wells Fargo and Bank of America | Line of Credit | Term Loan Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity									300,000
Amortization of financing costs		$ 7,500				$ 18,800
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member]
Line of Credit Facility [Line Items]
Maturity date			Jul. 21, 2021
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Commitment fee rate range			0.125%
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Commitment fee rate range			0.20%
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Scenario 3 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Covenant Terms			50.0
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Scenario 4 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Covenant Terms			75.0
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Adjusted LIBOR One | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate			0.00%
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Adjusted LIBOR One | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate			0.75%
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Adjusted LIBOR Two | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate			1.00%
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Adjusted LIBOR Two | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate			1.75%
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Line of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Outstanding borrowings			$ 231,000	$ 238,000
First Amendment To Credit Agreement [Member] | Wells Fargo and Bank of America | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity								$ 350,000
Line of Credit, Maximum Borrowing Capacity, Increase								50,000
First Amendment To Credit Agreement [Member] | Wells Fargo and Bank of America | Term Loan Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity								93,800
Outstanding borrowings								$ 93,800
Credit Agreement [Member] | Term Loan Facility
Line of Credit Facility [Line Items]
Maturity date		Dec. 03, 2019
Second Amendment To Credit Agreement [Member] [Domain] | WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. [Member] | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	500,000	$ 500,000	$ 850,000				$ 500,000
Note Purchase Agreement [Member]
Line of Credit Facility [Line Items]
Debt instrument costs							3,400
Capitalized debt issuance fees	2,000	2,000					2,000
Debt discount	$ 1,400	$ 1,400					$ 1,400
Note Purchase Agreement [Member] | Senior Notes
Line of Credit Facility [Line Items]
Senior notes									400,000
4.07% Senior Notes, Series A | Senior Notes
Line of Credit Facility [Line Items]
Senior notes									$ 100,000
Stated interest rate									4.07%
4.19% Senior Notes, Series B | Senior Notes
Line of Credit Facility [Line Items]
Senior notes									$ 100,000
Stated interest rate									4.19%
4.25% Senior Notes, Series C | Senior Notes
Line of Credit Facility [Line Items]
Senior notes									$ 100,000
Stated interest rate									4.25%
4.35% Senior Notes, Series D | Senior Notes
Line of Credit Facility [Line Items]
Senior notes									$ 100,000
Stated interest rate									4.35%