Stock-Based Awards - Narratives (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Oct. 27, 2018	Oct. 27, 2018	Jan. 27, 2018
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 2.9	$ 2.9
Total compensation cost not yet recognized, period for recognition	2 years 5 months
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 9.8	$ 9.8
Total compensation cost not yet recognized, period for recognition	2 years 6 months
Granted (in shares)		54,757
Shares outstanding	163,267	163,267	133,896
Shares canceled (in shares)		6,673
Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 22.0	$ 22.0
Total compensation cost not yet recognized, period for recognition	1 year 9 months 18 days
Compensation expense	$ 9.6	$ 9.6
RSUs outstanding (in shares)		158,841
Granted (in shares)		218,628
Shares outstanding	498,996	498,996	390,327
Shares canceled (in shares)	24,689	55,255
Target Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding	375,719	375,719
Supplemental Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		59,787
Shares outstanding	123,277	123,277

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

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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

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Unrecognized cost of unvested options awarded to employees as compensation.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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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).

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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.

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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.

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