Common shares, treasury shares, reserves and dividends - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018
Class of Stock [Line Items]
Common shares, par value (usd per share)	$ 0.18	$ 0.18
Proceeds from issuance of common shares	$ 1.0		$ 0.3
Treasury stock reissued (in shares)	400,000	200,000	300,000
Treasury shares retired (in shares)	0
Cumulative undeclared dividends	$ 0.0
Dividends on redeemable convertible preferred shares	32.9	$ 32.9	$ 32.9
Series A Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Dividends on redeemable convertible preferred shares	$ 1.7	$ 1.7	$ 1.7