Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Outstanding Ordinary Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]
Beginning Balance, Amount at Jan. 31, 2013	$ 112,332	$ 12	$ 91,911		$ 20,409
Beginning Balance, Shares at Jan. 31, 2013		27,035,074
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Amount	$ 6,920	$ 1	6,919
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Shares		1,160,286
Exercise of stock options, Shares	1,160,286
Vesting of early exercised stock options	$ 143		143
Vesting of restricted stock units, Shares		174,888
Employee stock purchase plan, Amount	1,744		1,744
Employee stock purchase plan, Shares		341,973
Exercise of warrants to purchase ordinary shares, Amount	130		130
Exercise of warrants to purchase ordinary shares, Shares		36,292
Stock-based compensation expense related to stock awards granted to employees and consultants	8,535		8,535
Excess income tax benefit associated with stock-based compensation	903		903
Net income	25,654				25,654
Ending Balance, Amount at Jan. 31, 2014	156,361	$ 13	110,285		46,063
Ending Balance, Shares at Jan. 31, 2014		28,748,513
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Amount	$ 8,508	$ 1	8,507
Exercise of stock options, dollar amounts net of unvested stock options exercised early, Shares		1,456,944
Exercise of stock options, Shares	1,456,944
Vesting of early exercised stock options	$ 59		59
Vesting of restricted stock units, Shares		484,296
Employee stock purchase plan, Amount	2,735		2,735
Employee stock purchase plan, Shares		147,776
Stock-based compensation expense related to stock awards granted to employees and consultants	15,692		15,692
Excess income tax benefit associated with stock-based compensation	3,286		3,286
Net unrealized gains (losses) on investments - net of taxes	(1)			$ (1)
Net income	50,571				50,571
Ending Balance, Amount at Jan. 31, 2015	$ 237,211	$ 14	140,564	(1)	96,634
Ending Balance, Shares at Jan. 31, 2015	30,837,529	30,837,529
Exercise of stock options, Amount	$ 5,176	$ 1	5,175
Exercise of stock options, Shares	567,888	567,888
Vesting of restricted stock and restricted stock units, Shares		848,756
Employee stock purchase plan, Amount	$ 3,100		3,100
Employee stock purchase plan, Shares		79,186
Stock-based compensation expense related to stock awards granted to employees and consultants	31,094		31,094
Excess income tax benefit associated with stock-based compensation	(3,627)		(3,627)
Net unrealized gains (losses) on investments - net of taxes	(6)			(6)
Net income	76,508				76,508
Ending Balance, Amount at Jan. 31, 2016	$ 349,456	$ 15	$ 176,306	$ (7)	$ 173,142
Ending Balance, Shares at Jan. 31, 2016	32,333,359	32,333,359