Common Shares, Treasury Shares, Reserves and Dividends - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended												9 Months Ended	12 Months Ended
	Feb. 03, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 29, 2017	Jan. 28, 2017	Oct. 29, 2016	Jul. 30, 2016	Apr. 30, 2016	Jan. 30, 2016	Oct. 31, 2015	Aug. 01, 2015	May 02, 2015	Oct. 29, 2016	Feb. 03, 2018	Jan. 28, 2017	Jan. 30, 2016
Class of Stock [Line Items]
Dividends declared per common share (usd per share)	$ 0.31	$ 0.31	$ 0.31	$ 0.31	$ 0.26	$ 0.26	$ 0.26	$ 0.26	$ 0.22	$ 0.22	$ 0.22	$ 0.22		$ 1.24	$ 1.04	$ 0.88
Cash dividend per share (usd per share)														$ 1.24	$ 1.04	$ 0.88
Total dividends	$ 18.8	$ 18.7	$ 18.7	$ 21.3	$ 17.7	$ 18.1	$ 19.7	$ 20.4	$ 17.5	$ 17.5	$ 17.6	$ 17.6		$ 77.5	$ 75.9	$ 70.2
Dividends on preferred shares	18.8				17.7									18.8	17.7
Series A Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Dividends, preferred stock, cash	$ 7.8	$ 7.8	$ 7.8	$ 7.8	$ 11.3	$ 0.0	$ 0.0	$ 0.0					$ 11.3	31.2
Accrued Expenses
Class of Stock [Line Items]
Dividends, preferred stock, cash														$ 7.8	$ 11.3