Components Of Equity - Additional Information (Detail) - $ / shares shares in Thousands		3 Months Ended
	May 07, 2019	Mar. 31, 2019	Mar. 31, 2018
Class of Stock [Line Items]
Expected common stock shares issued and outstanding		160,000
Non-Discretionary Plan
Class of Stock [Line Items]
Shares repurchased		88	446
Average price per share		$ 74.03	$ 65.68
Discretionary Plan
Class of Stock [Line Items]
Shares repurchased		500	2,216
Average price per share		$ 75.64	$ 64.58
Subsequent Event
Class of Stock [Line Items]
Date of declaration of dividends	May 07, 2019
Dividend declared per share	$ 0.50
Date of dividend payment	Jun. 17, 2019
Dividends payable to shareholders date of record	Jun. 03, 2019