Employee Benefits and Stock-based Compensation - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
	Oct. 31, 2012	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Voting power of all classes of company's shares		10.00%	10.00%	10.00%
Term of up to 10 years from grant date		10 years	10 years	10 years
Vesting period of stock options		Vest 25% on the first anniversary date of the grant and the remainder ratably over the following 36 months	Vest 25% on the first anniversary date of the grant and the remainder ratably over the following 36 months	Vest 25% on the first anniversary date of the grant and the remainder ratably over the following 36 months
Restricted stock units granted	344,671	345,171
Estimated fair value of restricted stock units, grant date	$ 9.99	$ 9.99
Vesting period of RSUs	1/16th of the RSUs shall vest each 3 months, 100% vest on the fourth anniversary date	1/16th of the RSUs shall vest each 3 months, 100% vest on the fourth anniversary date
Percentage of salary contribution by employees		10.00%
Percentage of purchase price of ordinary shares		85.00%
Unvested early exercised options, repurchased		84,377	76,982
Unvested shares subject to the Company's repurchase rights		53,151	122,064
Amount of income tax benefit recognized on stock-based compensation		$ 507,000	$ 473,000	$ 111,000
Income tax benefit recognized on stock-based compensation which is recorded in paid-in capital		7,000	125,000
Closing price of ordinary shares		$ 9.96
Aggregate intrinsic value of unvested restricted stock units		3,400,000
Non-employee stock-based compensation
Accelerate aggregate stock options			22,222
Additional stock-based compensation			206,000
Unvested stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost		7,300,000	9,500,000
Weighted-average period		2 years 3 months 4 days	2 years 8 months 12 days
Unvested restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost		$ 2,400,000
Weighted-average period		1 year 9 months 7 days
Incentive Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of stock options as percentage of fair market value at grant date		110.00%
Non Statutory Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of stock options as percentage of fair market value at grant date		100.00%