Components Of Equity - Additional Information (Detail) - $ / shares			6 Months Ended
	May. 06, 2015	May. 07, 2014	Jun. 30, 2015	Jun. 30, 2014	Aug. 04, 2015
Class of Stock [Line Items]
Date of declaration of dividends	May 06, 2015	May 07, 2014
Dividend declared per share	$ 0.36	$ 0.32
Date of dividend payment	Jun. 15, 2015	Jun. 16, 2014
Dividends payable to shareholders date of record	Jun. 01, 2015	Jun. 02, 2014
Non-Discretionary Plan
Class of Stock [Line Items]
Shares repurchased			1,183,284	651,982
Average price per share			$ 47.06	$ 44.26
Discretionary Plan
Class of Stock [Line Items]
Shares repurchased			3,132,992	7,947,500
Average price per share			$ 47.82	$ 41.43
Expected common stock shares issued and outstanding			188,000,000
Subsequent Event | Discretionary Plan
Class of Stock [Line Items]
Expected common stock shares issued and outstanding					180,000,000