Stock Repurchase Program - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended					4 Months Ended	6 Months Ended
	May 22, 2020	Feb. 29, 2020	Dec. 31, 2019	May 31, 2019	Apr. 30, 2020		Feb. 29, 2020	Apr. 30, 2019	[2]	May 22, 2020	Apr. 30, 2020		Apr. 30, 2019	[2]	Jun. 14, 2019
Accelerated Share Repurchases [Line Items]
Stock repurchase program authorized amount					$ 500.0						$ 500.0				$ 500.0
Remaining amount available for further repurchases					$ 200.0						$ 200.0
Purchases of treasury stock (in shares)					652,000	[1]		780,000			1,231,000	[1]	1,126,000
December 2019, ASR
Accelerated Share Repurchases [Line Items]
Stock repurchase program authorized amount			$ 100.0
Prepayment to repurchase stock			100.0
Initial share delivery			$ 80.0
Stock repurchase program, prepayment during prior period, derivative settlement		$ 20.0
Purchases of treasury stock (in shares)							700,000
Purchases of treasury stock							$ 149.75
February 2020, ASR
Accelerated Share Repurchases [Line Items]
Stock repurchase program authorized amount		100.0					$ 100.0
Prepayment to repurchase stock		100.0
Initial share delivery		$ 80.0					$ 80.0
February 2020, ASR | Subsequent Event
Accelerated Share Repurchases [Line Items]
Stock repurchase program, prepayment during prior period, derivative settlement	$ 20.0
Purchases of treasury stock (in shares)	148,953									700,000
Purchases of treasury stock										$ 140.41
February 2019, ASR
Accelerated Share Repurchases [Line Items]
Stock repurchase program, prepayment during prior period, derivative settlement				$ 20.0
Purchases of treasury stock (in shares)				97,601

[1] Does not include the 148,953 shares and $20.0 million equity forward contract, respectively, from the February 2020 ASR settled in May 2020.

[2] Does not include the 97,601 shares and $20.0 million equity forward contract, respectively, from the February 2019 ASR settled in May 2019.