Stock-Based Awards (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jan. 28, 2017	Jan. 28, 2017	Jul. 30, 2016
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 3.6	$ 3.6
Total compensation cost not yet recognized, period for recognition	2 years 11 months
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 10.5	$ 10.5
Total compensation cost not yet recognized, period for recognition	2 years 11 months
Granted (in shares)		60,485
Shares outstanding (in shares)	203,079	203,079	251,264
Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 24.1	$ 24.1
Total compensation cost not yet recognized, period for recognition	2 years 2 months
Compensation expense	$ 8.2	$ 8.2
RSUs outstanding (in shares)		198,140
Granted (in shares)		274,282
Shares outstanding (in shares)	559,531	559,531	625,971
Target Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)	418,939	418,939
Supplemental Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		76,142
Forfeited or cancelled (in shares)		49,797
Shares outstanding (in shares)	140,592	140,592

Potential Compensation Expense for Performance Based Shares If Performance Goals Are Met

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- Definition

Share-based compensation by share-based payment award, equity awards other than options, target amount of performance shares

+ References

No definition available.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Cancelled in Period

+ References

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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