Capital Stock - Additional Information (Detail) - USD ($)			3 Months Ended		35 Months Ended
	Feb. 01, 2019	Jun. 04, 2018	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Jan. 31, 2019
Class Of Stock [Line Items]
Preference shares, shares authorized			20,000,000		20,000,000	20,000,000
Preference shares, par value			$ 0.00045		$ 0.00045	$ 0.00045
Preference shares, shares issued			0		0	0
Preference shares, shares outstanding			0		0	0
Ordinary shares, shares authorized			200,000,000		200,000,000	200,000,000
Stock repurchased during period, shares			0		3,985,876
Stock repurchased during period, cash			$ 0	$ 20,624,000	$ 174,800,000
2012 Equity Incentive Plan [Member]
Class Of Stock [Line Items]
Additional ordinary shares reserved for issuance	1,453,659
2012 Equity Incentive Plan [Member] | Scenario, plan automatically increased by the lessor of [Member]
Class Of Stock [Line Items]
Annual increase in ordinary shares for available for future issuance	3,500,000
Annual shares increase for future issuance by percentage under 2012 equity incentive plan	4.50%
Amended and Restated 2012 Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Additional ordinary shares reserved for issuance	403,794
Amended and Restated 2012 Employee Stock Purchase Plan [Member] | Scenario, plan automatically increased by the lessor of [Member]
Class Of Stock [Line Items]
Annual increase in ordinary shares for available for future issuance	1,500,000
Annual shares increase for future issuance by percentage under 2012 employee stock purchase plan	1.25%
Stock Repurchase Program $100.0 Million Authorization [Member]
Class Of Stock [Line Items]
Stock repurchase program, authorization date		Jun. 04, 2018
Stock repurchase program, period		12 months
Stock repurchase program, commencing date		Jun. 05, 2018
Stock Repurchase Program $100.0 Million Authorization [Member] | Maximum [Member]
Class Of Stock [Line Items]
Amount authorized under stock repurchase program		$ 100,000,000