Other assets - Components of Other Assets (Detail) (USD $) In Millions, unless otherwise specified	May 02, 2015	Jan. 31, 2015	May 03, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred extended service plan costs	$ 71.5	$ 69.7	$ 63.6
Investments	23.0us-gaap_Investments	25.2us-gaap_Investments	0us-gaap_Investments
Other assets	46.6	45.1	29.9
Total other assets	141.1us-gaap_OtherAssetsNoncurrent	140.0us-gaap_OtherAssetsNoncurrent	93.5us-gaap_OtherAssetsNoncurrent
Deferred costs related to the sale of the extended service plan	$ 26.8	$ 24.9	$ 22.5

Deferred Costs, Sale of Extended Service Plan

No definition available.

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- Definition

Deferred Revenue Extended Service Plan Costs Noncurrent

+ References

No definition available.

+ Details

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- Details

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- Definition

Sum of the carrying amounts as of the balance sheet date of all investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(h))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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- Definition

Amount of other miscellaneous assets expected to be realized or consumed after one year or normal operating cycle, if longer.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherAssetsMiscellaneousNoncurrent
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- Definition

Aggregate carrying amount, as of the balance sheet date, of noncurrent assets not separately disclosed in the balance sheet. Noncurrent assets are expected to be realized or consumed after one year (or the normal operating cycle, if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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