Components Of Equity - Additional Information (Detail) - $ / shares shares in Thousands				9 Months Ended
	Nov. 08, 2016	May 03, 2016	May 06, 2015	Sep. 30, 2016	Sep. 30, 2015
Class of Stock [Line Items]
Date of declaration of dividends		May 03, 2016	May 06, 2015
Dividend declared per share		$ 0.40	$ 0.36
Date of dividend payment		Jun. 15, 2016	Jun. 15, 2015
Dividends payable to shareholders date of record		Jun. 01, 2016	Jun. 01, 2015
Non-Discretionary Plan
Class of Stock [Line Items]
Shares repurchased				2,822	2,243
Average price per share				$ 49.84	$ 47.93
Discretionary Plan
Class of Stock [Line Items]
Shares repurchased				2,579	6,396
Average price per share				$ 49.41	$ 48.16
Expected common stock shares issued and outstanding				170,000
Subsequent Event
Class of Stock [Line Items]
Date of declaration of dividends	Nov. 08, 2016
Dividend declared per share	$ 0.40
Date of dividend payment	Dec. 15, 2016
Dividends payable to shareholders date of record	Dec. 01, 2016