Stock Repurchase Program - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands	1 Months Ended				3 Months Ended
	Feb. 23, 2018	Dec. 31, 2017	Nov. 30, 2017	Sep. 30, 2017	May 16, 2018	Jan. 31, 2018	Nov. 30, 2017	Jan. 31, 2017	Jun. 15, 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program authorized amount						$ 500,000,000			$ 500,000,000
Remaining amount available for further repurchases						$ 200,000,000
Shares repurchased (in shares)						1,987		1,393
Accelerated Share Repurchase Program September 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program authorized amount				$ 100,000,000.0
Prepayment amount				100,000,000.0
Accelerated share repurchase, initial share delivery, amount				$ 80,000,000.0
Stock repurchase program, prepayment during prior period, derivative settlement			$ 20,000,000.0
Shares repurchased (in shares)							1,200
Average purchase price of shares purchased under agreement (in USD per share)							$ 83.80
Accelerated Share Repurchase Program December 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program authorized amount		$ 200,000,000.0
Prepayment amount		200,000,000.0
Accelerated share repurchase, initial share delivery, amount		$ 160,000,000.0
Subsequent Event [Member] | Accelerated Share Repurchase Program December 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, prepayment during prior period, derivative settlement	$ 20,000,000
Scenario, Forecast | Accelerated Share Repurchase Program December 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, prepayment during prior period, derivative settlement					$ 20,000,000.0