Common Shares, Treasury Shares, Reserves and Dividends - Additional Information (Detail) - USD ($)			1 Months Ended	3 Months Ended												12 Months Ended
	Mar. 01, 2018	Oct. 05, 2016	Dec. 31, 2016	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	Feb. 03, 2018	Jan. 28, 2017	Jan. 30, 2016	Jun. 30, 2017	Aug. 31, 2016	Feb. 29, 2016
Class of Stock [Line Items]
Common shares, par value (usd per share)				$ 0.18				$ 0.18								$ 0.18	$ 0.18
Proceeds from issuance of common shares																$ 300,000	$ 2,100,000	$ 5,000,000
Shares repurchased (shares)																8,100,000	11,200,000	1,000,000
Amount repurchased																$ 460,000,000	$ 1,000,000,000	$ 130,000,000
Average repurchase price per share (usd per share)																$ 56.91	$ 89.10	$ 127.63
Treasury stock held (shares)				26,700,000				18,900,000								26,700,000	18,900,000
Treasury stock reissued																300,000	100,000
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
Dividends on preferred shares				$ 18,800,000				$ 17,700,000								$ 18,800,000	$ 17,700,000
Cumulative undeclared dividends																0
Dividends on redeemable convertible preferred shares																32,900,000	$ 11,900,000
Subsequent Event
Class of Stock [Line Items]
Dividends declared date	Mar. 14, 2018
Dividends declared per common share (usd per share)	$ 0.37
Dividends payable date	Jun. 01, 2018
Dividends payable, date of record	May 04, 2018
2016 Program
Class of Stock [Line Items]
Amount authorized				1,375,000,000												$ 1,375,000,000				$ 625,000,000	$ 750,000,000
Shares repurchased (shares)																8,082,630	10,004,333
Amount repurchased																$ 460,000,000	$ 864,400,000
Average repurchase price per share (usd per share)																$ 56.91	$ 86.40
Accelerated Share Repurchase Program
Class of Stock [Line Items]
Accelerated share repurchases, payment		$ 525,000,000
Shares repurchased (shares)		4,700,000	1,300,000													6,000,000
Amount repurchased		$ 367,500,000
Average repurchase price per share (usd per share)																$ 87.01
2017 Program
Class of Stock [Line Items]
Amount authorized				$ 650,600,000												$ 650,600,000			$ 600,000,000.0
Series A Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Dividends on redeemable convertible preferred shares																$ 1,700,000	$ 600,000