Components Of Equity - Additional Information (Detail) - $ / shares shares in Thousands				9 Months Ended
	Nov. 07, 2017	May 02, 2017	May 03, 2016	Sep. 30, 2017	Sep. 30, 2016
Class of Stock [Line Items]
Date of declaration of dividends		May 02, 2017	May 03, 2016
Dividend declared per share		$ 0.42	$ 0.40
Date of dividend payment		Jun. 15, 2017	Jun. 15, 2016
Dividends payable to shareholders date of record		Jun. 01, 2017	Jun. 01, 2016
Non-Discretionary Plan
Class of Stock [Line Items]
Shares repurchased				2,902	2,822
Average price per share				$ 55.58	$ 49.84
Discretionary Plan
Class of Stock [Line Items]
Shares repurchased				3,189	2,579
Average price per share				$ 56.26	$ 49.41
Expected common stock shares issued and outstanding				170,000
Subsequent Event
Class of Stock [Line Items]
Date of declaration of dividends	Nov. 07, 2017
Dividend declared per share	$ 0.42
Date of dividend payment	Dec. 15, 2017
Dividends payable to shareholders date of record	Dec. 01, 2017