Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Outstanding Ordinary Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Beginning Balance, Amount at Jan. 31, 2017	$ 454,634	$ 15	$ 212,276	$ (70)	$ 242,413
Beginning Balance, Shares at Jan. 31, 2017		33,369,032
Exercise of stock options, Amount	$ 2,191	$ 0	2,191	0	0
Exercise of stock options, Shares	175,187	175,187
Vesting of restricted stock units, Amount	$ 0	$ 0	0	0	0
Vesting of restricted stock units, Shares		932,454
Employee stock purchase plan, Amount	4,646	$ 0	4,646	0	0
Employee stock purchase plan, Shares		107,736
Stock repurchase, Amount	(54,788)	$ 0	(54,788)	0	0
Stock repurchase, Shares		(1,094,795)
Stock-based compensation expense related to stock awards granted to employees and consultants	56,861	$ 0	56,861	0	0
Net unrealized gains (losses) on investments - net of taxes	(209)	0	0	(209)	0
Net income (loss)	18,852	0	0	0	18,852
Ending Balance, Amount at Jan. 31, 2018	482,187	$ 15	221,186	(279)	261,265
Ending Balance, Shares at Jan. 31, 2018		33,489,614
Cumulative Effect of Change in Accounting Principle	43	$ 0	0	0	43
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 (losses) on investments - net of taxes	376	0	0	376	0
Net income (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	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 repurchase, Shares	0
Stock-based compensation expense related to stock awards granted to employees and consultants	$ 61,042	$ 0	61,042	0	0
Net unrealized gains (losses) on investments - net of taxes	671	0	0	671	0
Net income (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