Income taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Jul. 31, 2021	May 02, 2020
Income Tax Disclosure [Abstract]
Tax benefit for release of valuation allowance	$ 49.8
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

CARES Act, Income Tax Expense (Benefit) on Net Operating Losses

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- Definition

CARES Act, Income Tax Expense (Benefit) on Tax Cuts and Jobs Act

+ References

No definition available.

+ Details

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- References

No definition available.

+ Details

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- Definition

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319

+ Details

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32537-109319

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