Long-Term Debt (Details) - USD ($) $ in Millions				3 Months Ended		4 Months Ended
	Oct. 31, 2020	Jul. 21, 2016	Mar. 15, 2016	Oct. 31, 2020	Oct. 31, 2020	Jul. 21, 2016	Jul. 31, 2020	Jul. 31, 2016	Dec. 03, 2014
Line of Credit Facility [Line Items]
Maturity date						Mar. 15, 2021
Applicable interest rate added to reference rate in order to compute variable interest rate					1.50%
Scenario 3
Line of Credit Facility [Line Items]
Long-term Debt					not to exceed $50.0 million
Scenario 4
Line of Credit Facility [Line Items]
Long-term Debt					not less than $75.0 million
Credit Agreement | Term Loan Facility
Line of Credit Facility [Line Items]
Maturity date						Dec. 03, 2019
Note Purchase Agreement | Senior Notes
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount									$ 400.0
Note Purchase Agreement | Senior Notes, Series A
Line of Credit Facility [Line Items]
Debt instrument, interest rate									4.07%
Note Purchase Agreement | Senior Notes, Series B
Line of Credit Facility [Line Items]
Debt instrument, interest rate									4.19%
Note Purchase Agreement | Senior Notes, Series C
Line of Credit Facility [Line Items]
Debt instrument, interest rate									4.25%
Note Purchase Agreement | Senior Notes, Series D
Line of Credit Facility [Line Items]
Debt instrument, interest rate									4.35%
Senior Notes, Series A [Member] | Senior Notes
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount									$ 100.0
Senior Notes, Series B [Member] | Senior Notes
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount									100.0
Senior Notes, Series C [Member] | Senior Notes
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount									100.0
Senior Notes, Series D [Member] | Senior Notes
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount									100.0
Eurodollar [Member] | Minimum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate	0.75%			0.75%
Wells Fargo and Bank of America, N.A. | Line of Credit
Line of Credit Facility [Line Items]
Repayments of Lines of Credit		$ 242.5
Wells Fargo and Bank of America, N.A. | Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity									300.0
Wells Fargo and Bank of America, N.A. | Credit Agreement | Term Loan Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity									$ 300.0
Wells Fargo and Bank of America, N.A. | First Amendment To Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 350.0
Line of Credit Facility, Increase (Decrease), Net			50.0
Wells Fargo and Bank of America, N.A. | First Amendment To Credit Agreement | Term Loan Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 93.8
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. | Revolving Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Outstanding borrowings	$ 0.0			$ 0.0	$ 0.0		$ 0.0
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. | Scenario 3
Line of Credit Facility [Line Items]
Line of Credit Facility, Covenant Terms					not to exceed $50.0 million
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. | Scenario 4
Line of Credit Facility [Line Items]
Line of Credit Facility, Covenant Terms					not less than $75.0 million
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. | Second Amendment To Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 500.0				$ 500.0		$ 850.0
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. | Federal Funds Effective Swap Rate | Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate					0.50%
WellsFargo,NationalAssociation,SunTrustBankandBankofAmerica,N.A. | Eurodollar [Member] | Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate					1.00%
WellsFargo,NationalAssociation,TruistBank,BMOHarrisBankN.A.,SantanderBankN.A.,andBankofAmerica,N.A. [Member]
Line of Credit Facility [Line Items]
Maturity date					Jul. 21, 2023
WellsFargo,NationalAssociation,TruistBank,BMOHarrisBankN.A.,SantanderBankN.A.,andBankofAmerica,N.A. [Member] | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Line of Credit Facility, Commitment Fee Percentage				0.25%
WellsFargo,NationalAssociation,TruistBank,BMOHarrisBankN.A.,SantanderBankN.A.,andBankofAmerica,N.A. [Member] | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Line of Credit Facility, Commitment Fee Percentage				0.35%
WellsFargo,NationalAssociation,TruistBank,BMOHarrisBankN.A.,SantanderBankN.A.,andBankofAmerica,N.A. [Member] | First Amended and Restated Credit Agreement [Member] | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,050.0			$ 1,050.0	$ 1,050.0
Line of Credit Facility, Increase (Decrease), Net				$ 200.0
WellsFargo,NationalAssociation,TruistBank,BMOHarrisBankN.A.,SantanderBankN.A.,andBankofAmerica,N.A. [Member] | Eurodollar [Member] | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate				1.50%
WellsFargo,NationalAssociation,TruistBank,BMOHarrisBankN.A.,SantanderBankN.A.,andBankofAmerica,N.A. [Member] | Eurodollar [Member] | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate				2.25%
WellsFargo,NationalAssociation,TruistBank,BMOHarrisBankN.A.,SantanderBankN.A.,andBankofAmerica,N.A. [Member] | Base Rate [Member] | Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate				0.50%
WellsFargo,NationalAssociation,TruistBank,BMOHarrisBankN.A.,SantanderBankN.A.,andBankofAmerica,N.A. [Member] | Base Rate [Member] | Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Applicable interest rate added to reference rate in order to compute variable interest rate				1.25%