Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Outstanding Ordinary Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]
Beginning Balance, Amount at Jan. 31, 2019	$ 419,489	$ 15	$ 188,516	$ 97	$ 230,861
Beginning Balance, Shares at Jan. 31, 2019		32,303,540
Issuance of shares through employee equity incentive plan, Amount	1,520	$ 0	1,520	0	0
Issuance of shares through employee equity incentive plan, Shares		335,301
Issuance of shares through employee stock purchase plan, Amount	3,063	$ 0	3,063	0	0
Issuance of shares through employee stock purchase plan, Shares		99,759
Stock-based compensation expense related to stock awards granted to employees and consultants	15,423	$ 0	15,423	0	0
Net unrealized gains (losses) on investments - net of taxes	254	0	0	254	0
Net loss	(17,311)	0	0	0	(17,311)
Ending Balance, Amount at Apr. 30, 2019	422,438	$ 15	208,522	351	213,550
Ending Balance, Shares at Apr. 30, 2019		32,738,600
Beginning Balance, Amount at Jan. 31, 2019	419,489	$ 15	188,516	97	230,861
Beginning Balance, Shares at Jan. 31, 2019		32,303,540
Net unrealized gains (losses) on investments - net of taxes	448
Net loss	(27,502)
Ending Balance, Amount at Jul. 31, 2019	428,461	$ 15	224,542	545	203,359
Ending Balance, Shares at Jul. 31, 2019		33,033,619
Beginning Balance, Amount at Apr. 30, 2019	422,438	$ 15	208,522	351	213,550
Beginning Balance, Shares at Apr. 30, 2019		32,738,600
Issuance of shares through employee equity incentive plan, Amount	988	$ 0	988	0	0
Issuance of shares through employee equity incentive plan, Shares		295,019
Stock-based compensation expense related to stock awards granted to employees and consultants	15,032	$ 0	15,032	0	0
Net unrealized gains (losses) on investments - net of taxes	194	0	0	194	0
Net loss	(10,191)	0	0	0	(10,191)
Ending Balance, Amount at Jul. 31, 2019	428,461	$ 15	224,542	545	203,359
Ending Balance, Shares at Jul. 31, 2019		33,033,619
Beginning Balance, Amount at Jan. 31, 2020	$ 448,072	$ 15	261,220	768	186,069
Beginning Balance, Shares at Jan. 31, 2020	33,805,609	33,805,609
Issuance of shares through employee equity incentive plan, Amount	$ 6,463	$ 0	6,463	0	0
Issuance of shares through employee equity incentive plan, Shares		478,643
Issuance of shares through employee stock purchase plan, Amount	2,660	$ 0	2,660	0	0
Issuance of shares through employee stock purchase plan, Shares		83,564
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	15,214	$ 0	15,214	0	0
Net unrealized gains (losses) on investments - net of taxes	(363)	0	0	(363)	0
Net loss	(15,463)	0	0	0	(15,463)
Ending Balance, Amount at Apr. 30, 2020	455,583	$ 15	284,557	405	170,606
Ending Balance, Shares at Apr. 30, 2020		34,342,097
Beginning Balance, Amount at Jan. 31, 2020	$ 448,072	$ 15	261,220	768	186,069
Beginning Balance, Shares at Jan. 31, 2020	33,805,609	33,805,609
Net unrealized gains (losses) on investments - net of taxes	$ 819
Net loss	(30,219)
Ending Balance, Amount at Jul. 31, 2020	$ 458,647	$ 15	301,195	1,587	155,850
Ending Balance, Shares at Jul. 31, 2020	34,610,836	34,610,836
Beginning Balance, Amount at Apr. 30, 2020	$ 455,583	$ 15	284,557	405	170,606
Beginning Balance, Shares at Apr. 30, 2020		34,342,097
Issuance of shares through employee equity incentive plan, Amount	344	$ 0	344	0	0
Issuance of shares through employee equity incentive plan, Shares		268,739
Stock-based compensation expense related to stock awards granted to employees and consultants	16,294	$ 0	16,294	0	0
Net unrealized gains (losses) on investments - net of taxes	1,182	0	0	1,182	0
Net loss	(14,756)	0	0	0	(14,756)
Ending Balance, Amount at Jul. 31, 2020	$ 458,647	$ 15	$ 301,195	$ 1,587	$ 155,850
Ending Balance, Shares at Jul. 31, 2020	34,610,836	34,610,836