Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Name:	us-gaap_DeferredIncomeTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Income taxes - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended		12 Months Ended
	Nov. 04, 2018	May 05, 2018	Aug. 04, 2018	Jul. 29, 2017	Nov. 03, 2018
Tax Credit Carryforward [Line Items]
Effective income tax rate, percent			20.00%	23.50%
Provisional benefit		$ 0.6	$ (0.3)	$ 2.6
Forecast
Tax Credit Carryforward [Line Items]
Effective income tax rate, percent	21.00%				23.40%