Components Of Equity - Additional Information (Detail) - $ / shares shares in Thousands			6 Months Ended
	May 08, 2018	May 02, 2017	Jun. 30, 2018	Jun. 30, 2017
Class of Stock [Line Items]
Date of declaration of dividends	May 08, 2018	May 02, 2017
Dividend declared per share	$ 0.45	$ 0.42
Date of dividend payment	Jun. 15, 2018	Jun. 15, 2017
Dividends payable to shareholders date of record	Jun. 01, 2018	Jun. 01, 2017
Non-Discretionary Plan
Class of Stock [Line Items]
Shares repurchased			1,441	1,651
Average price per share			$ 72.21	$ 55.74
Discretionary Plan
Class of Stock [Line Items]
Shares repurchased			4,311	831
Average price per share			$ 70.49	$ 55.27
Expected common stock shares issued and outstanding			170,000