Redeemable preferred shares - Additional Information (Details) - Series A Redeemable Convertible Preferred Stock - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Oct. 05, 2016	May 01, 2021	May 02, 2020	Jan. 30, 2021
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued (shares)	625,000
Preferred stock, purchase price	$ 625.0
Shares issued, price per share (in usd per share)	$ 1,000
Preferred stock, dividend rate, percentage		5.00%
Preferred stock, increase in stated value (in usd per share)		$ 12.97
Payments of stock issuance costs	$ 13.7
Accumulated accretion of dividends		$ 7.7	$ 6.1	$ 7.3
Accretion on redeemable convertible preferred shares		$ 0.4	$ 0.4