Accounts receivable - Additional Information (Details) - Credit Transaction, Net - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Aug. 04, 2018	Aug. 04, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Valuation losses on accounts receivable	$ 19.4	$ 160.4
Other transacted-related costs	$ 4.5	$ 6.6

Amount of expense related to write-down of receivables to the amount expected to be collected. Includes, but is not limited to, accounts receivable and notes receivable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.5)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130534-203044

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration