Common Shares, Treasury Shares, Reserves and Dividends - Additional Information (Detail) - USD ($)			1 Months Ended	3 Months Ended												12 Months Ended
	Feb. 28, 2019	Oct. 05, 2016	Dec. 31, 2016	Feb. 02, 2019	Aug. 04, 2018	May 05, 2018	Feb. 03, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 29, 2017	Oct. 29, 2016	Jan. 30, 2016	Oct. 31, 2015	Aug. 01, 2015	May 02, 2015	Feb. 02, 2019	Feb. 03, 2018	Jan. 28, 2017	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																$ 0	$ 300,000	$ 2,100,000
Shares repurchased (shares)																8,800,000	8,100,000	11,200,000
Amount repurchased																$ 485,000,000	$ 460,000,000	$ 1,000,000,000
Average repurchase price per share (usd per share)																$ 55.06	$ 56.91	$ 89.10
Treasury stock reissued																200,000	300,000
Treasury shares retired																17,200,000
Dividends on preferred shares				$ 19,200,000			$ 18,800,000									$ 19,200,000	$ 18,800,000
Dividends declared per common share (usd per share)				$ 0.37	$ 0.37	$ 0.37	$ 0.31	$ 0.37	$ 0.31	$ 0.31	$ 0.31	$ 0.26	$ 0.26	$ 0.26	$ 0.26	$ 1.48	$ 1.24	$ 1.04
Cumulative undeclared dividends																$ 0
Dividends on redeemable convertible preferred shares																32,900,000	$ 32,900,000	$ 11,900,000
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)																1,272,176	8,082,630	10,004,333
Amount repurchased																$ 50,600,000	$ 460,000,000	$ 864,400,000
Average repurchase price per share (usd per share)																$ 39.76	$ 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				$ 600,000,000												$ 600,000,000			$ 600,000,000
Shares repurchased (shares)																7,537,062
Amount repurchased																$ 434,400,000
Average repurchase price per share (usd per share)																$ 57.64
Series A Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Dividends on redeemable convertible preferred shares																$ 1,700,000	$ 1,700,000
Subsequent Event
Class of Stock [Line Items]
Dividends declared date	Feb. 28, 2019
Dividends declared per common share (usd per share)	$ 0.37
Dividends payable date	May 31, 2019
Dividends payable, date of record	May 03, 2019