Share-based compensation - Summary of Activity of Awards Granted under Share Saving Plan (Details) - Saving Share Plans - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
Feb. 02, 2019	Feb. 03, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance (shares)	0.3
Granted (shares)	0.0
Exercised (shares)	0.0
Lapsed (shares)	(0.1)
Ending Balance (shares)	0.2	0.3
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning Balance (usd per share)	$ 62.80
Granted (usd per share)	57.97
Exercised (usd per share)	57.80
Lapsed (usd per share)	65.42
Ending Balance (usd per share)	$ 54.80	$ 62.80
Weighted average remaining contractual life	1 year 6 months	21 months
Intrinsic value	$ 0.0	$ 0.0
Shares Exercisable (shares)	0.0	0.0
Weighted Average Exercise Price, Shares Exercisable (usd per share)	$ 0.00	$ 0.00
Intrinsic Value, Shares Exercisable	$ 0.0	$ 0.0

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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- Definition

For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Net number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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No definition available.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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No definition available.

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- Definition

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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- Definition

Weighted average grant-date fair value of non-vested options forfeited.

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No definition available.

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- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Number of share options (or share units) exercised during the current period.

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