Capital Stock - Additional Information (Detail) - USD ($)				3 Months Ended	6 Months Ended
	May 29, 2019	Feb. 01, 2019	Jun. 04, 2018	Jul. 31, 2019	Jul. 31, 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	0
Amount available under stock repurchase program				$ 50,000,000.0	$ 50,000,000.0
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, expiration date			Jun. 04, 2019
Stock Repurchase Program $100.0 Million Authorization [Member] | Maximum [Member]
Class Of Stock [Line Items]
Amount authorized under stock repurchase program			$ 100,000,000.0
Stock Repurchase Program $50.0 Million Authorization [Member]
Class Of Stock [Line Items]
Stock repurchase program, authorization date	May 29, 2019
Stock repurchase program, expiration date	Jun. 30, 2020
Stock Repurchase Program $50.0 Million Authorization [Member] | Maximum [Member]
Class Of Stock [Line Items]
Amount authorized under stock repurchase program	$ 50,000,000.0