Stock-based Compensation (Summary of Total Compensation Expense and Associated Income Tax Benefit) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
May 02, 2020	May 04, 2019	May 02, 2020	May 04, 2019
Share-based Payment Arrangement [Abstract]
Compensation expense	$ 0.8	$ 2.2	$ 3.2	$ 10.5
Income tax benefit	$ 0.0	$ 0.5	$ 0.0	$ 2.2

Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

Name:	us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration