Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect of Change in Accounting Principle [Member]	Outstanding Ordinary Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect of Change in Accounting Principle [Member]
Beginning Balance, Amount at Jan. 31, 2018	$ 482,187	$ 43	$ 15	$ 221,186	$ (279)	$ 261,265	$ 43
Beginning Balance, Shares at Jan. 31, 2018			33,489,614
Exercise of stock options, Amount	$ 1,285		$ 0	1,285	0	0
Exercise of stock options, Shares	232,205		232,205
Vesting of restricted stock units, Amount	$ 0		$ 0	0	0	0
Vesting of restricted stock units, Shares			920,826
Employee stock purchase plan, Amount	5,136		$ 0	5,136	0	0
Employee stock purchase plan, Shares			146,887
Stock repurchase, Amount	(99,903)		$ 0	(99,903)	0	0
Stock repurchase, Shares			(2,485,992)
Stock-based compensation expense related to stock awards granted to employees and consultants	60,812		$ 0	60,812	0	0
Net unrealized gains on investments - net of tax	376		0	0	376	0
Net loss	(30,447)		0	0	0	(30,447)
Ending Balance, Amount at Jan. 31, 2019	419,489		$ 15	188,516	97	230,861
Ending Balance, Shares at Jan. 31, 2019			32,303,540
Exercise of stock options, Amount	$ 5,695		$ 0	5,695	0	0
Exercise of stock options, Shares	366,886		366,886
Vesting of restricted stock units, Amount	$ 0		$ 0	0	0	0
Vesting of restricted stock units, Shares			957,319
Employee stock purchase plan, Amount	5,967		$ 0	5,967	0	0
Employee stock purchase plan, Shares			177,864
Stock-based compensation expense related to stock awards granted to employees and consultants	61,042		$ 0	61,042	0	0
Net unrealized gains on investments - net of tax	671		0	0	671	0
Net loss	(44,792)		0	0	0	(44,792)
Ending Balance, Amount at Jan. 31, 2020	$ 448,072		$ 15	261,220	768	186,069
Ending Balance, Shares at Jan. 31, 2020	33,805,609		33,805,609
Exercise of stock options, Amount	$ 10,333		$ 0	10,333	0	0
Exercise of stock options, Shares	421,736		421,736
Vesting of restricted stock units, Amount	$ 5,351		$ 1	5,350	0	0
Vesting of restricted stock units, Shares			1,162,883
Employee stock purchase plan, Amount	5,825		$ 0	5,825	0	0
Employee stock purchase plan, Shares			182,931
Stock repurchase, Amount	(1,000)		$ 0	(1,000)	0	0
Stock repurchase, Shares			(25,719)
Stock-based compensation expense related to stock awards granted to employees and consultants	65,730		$ 0	65,730	0	0
Net unrealized gains on investments - net of tax	451		0	0	451	0
Net loss	(59,786)		0	0	0	(59,786)
Ending Balance, Amount at Jan. 31, 2021	$ 474,976		$ 16	$ 347,458	$ 1,219	$ 126,283
Ending Balance, Shares at Jan. 31, 2021	35,547,440		35,547,440