Revenue recognition - ESP Deferred Revenue Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
May 04, 2019	May 05, 2018
Change in Contract with Customer, Liability [Roll Forward]
ESP deferred revenue, beginning of period	$ 966.5
ESP deferred revenue, end of period	976.6	$ 952.4
Extended Service Plan
Change in Contract with Customer, Liability [Roll Forward]
ESP deferred revenue, beginning of period	927.6	916.1
Plans sold	92.3	98.6
Revenue recognized	96.0	96.0
ESP deferred revenue, end of period	$ 931.3	$ 913.5

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130532-203044

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant