Common shares, treasury shares, reserves and dividends - Share Repurchase (Details) - USD ($)	12 Months Ended
	Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018	Jun. 30, 2017
Class of Stock [Line Items]
Shares repurchased (shares)	0	8,800,000	8,100,000
Amount repurchased	$ 0	$ 485,000,000.0	$ 460,000,000.0
Average repurchase price per share (usd per share)	$ 0	$ 55.06	$ 56.91
2017 Program
Class of Stock [Line Items]
Amount authorized	$ 600,000,000.0			$ 600,000,000.0
Shares repurchased (shares)	0	7,500,000
Amount repurchased	$ 0	$ 434,400,000
Average repurchase price per share (usd per share)	$ 0	$ 57.64
Remaining authorized repurchase amount	$ 165,600,000
2016 Program
Class of Stock [Line Items]
Amount authorized	$ 1,375,000,000.0
Shares repurchased (shares)		1,300,000	8,100,000
Amount repurchased		$ 50,600,000	$ 460,000,000.0
Average repurchase price per share (usd per share)		$ 39.76	$ 56.91