Income taxes - Narrative (Details) $ in Millions	3 Months Ended
May 02, 2020 USD ($)
Income Tax Disclosure [Abstract]
CARES Act, income tax benefit on Tax Cuts and Jobs Act	$ 67.5
CARES Act, income tax benefit on net operating losses	48.5
Increase in valuation allowance	$ 56.7

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=116821951&loc=d3e32123-109318

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Balance Type:	credit
Period Type:	duration