Stock Repurchase Program - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands	1 Months Ended						3 Months Ended		4 Months Ended	6 Months Ended	12 Months Ended
	Oct. 31, 2018	May 31, 2018	Mar. 31, 2018	Feb. 28, 2018	Dec. 31, 2017	Sep. 30, 2017	Jan. 31, 2018	Nov. 30, 2017	Mar. 31, 2018	Oct. 31, 2018	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016	Apr. 05, 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program authorized amount	$ 500,000,000.0									$ 500,000,000.0	$ 500,000,000.0			$ 500,000,000
Remaining amount available for further repurchases	325,000,000									$ 325,000,000	$ 325,000,000
Purchases of treasury stock (in shares)											4,688	5,413	8,506
Average purchase price (in USD per share)											$ 89.59	$ 70.21	$ 49.37
Accelerated Share Repurchase Program September 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program authorized amount						$ 100,000,000.0
Stock repurchase program, prepayment during period						100,000,000
Accelerated share repurchase, initial share delivery, amount						$ 80,000,000
Stock repurchase program, prepayment during period, derivative settlement							$ 20,000,000
Purchases of treasury stock (in shares)								1,200
Average purchase price (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
Stock repurchase program, prepayment during period					200,000,000
Accelerated share repurchase, initial share delivery, amount					$ 160,000,000
Stock repurchase program, prepayment during period, derivative settlement			$ 20,000,000	$ 20,000,000
Purchases of treasury stock (in shares)									2,300
Average purchase price (in USD per share)									$ 87.08
Accelerated Share Repurchase Program May 2018
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program authorized amount		$ 165,000,000.0
Stock repurchase program, prepayment during period		165,000,000
Accelerated share repurchase, initial share delivery, amount		$ 132,000,000
Stock repurchase program, prepayment during period, derivative settlement	$ 33,000,000
Purchases of treasury stock (in shares)										1,800
Average purchase price (in USD per share)										$ 92.42