Shareholders' Equity - Additional Information (Detail) - $ / shares shares in Thousands				9 Months Ended
	Nov. 04, 2019	May 07, 2019	May 08, 2018	Sep. 30, 2019	Sep. 30, 2018
Class of Stock [Line Items]
Expected common stock shares issued and outstanding				160,000
Date of declaration of dividends		May 07, 2019	May 08, 2018
Dividend declared per share		$ 0.50	$ 0.45
Date of dividend payment		Jun. 17, 2019	Jun. 15, 2018
Dividends payable to shareholders date of record		Jun. 03, 2019	Jun. 01, 2018
Subsequent Event
Class of Stock [Line Items]
Date of declaration of dividends	Nov. 04, 2019
Dividend declared per share	$ 0.50
Date of dividend payment	Dec. 16, 2019
Dividends payable to shareholders date of record	Dec. 02, 2019
Discretionary Plan
Class of Stock [Line Items]
Shares repurchased				4,002	5,378
Average price per share				$ 72.57	$ 71.07
Non-Discretionary Plan
Class of Stock [Line Items]
Shares repurchased				88	2,386
Average price per share				$ 74.03	$ 72.72