CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Retained Earnings
Beginning balance (in shares) at Jan. 31, 2020		278,731,143
Beginning balance at Jan. 31, 2020	$ 833,943	$ 277	$ 832,705	$ 809	$ 152
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		4,830,752
Issuance of common stock upon exercise of stock options	17,681	$ 5	17,676
Issuance of common stock upon release of restricted stock units (in shares)		174,900
Issuance of common stock for employee stock purchase plan (in shares)		605,924
Issuance of common stock for employee stock purchase plan	20,760	$ 1	20,759
Charitable donation of common stock	23,312		23,312
Stock-based compensation expense	88,089		88,089
Other comprehensive income (loss)	1,963			1,963
Net income	213,064				213,064
Ending balance (in shares) at Jul. 31, 2020		284,342,719
Ending balance at Jul. 31, 2020	1,198,812	$ 283	982,541	2,772	213,216
Beginning balance (in shares) at Apr. 30, 2020		281,992,011
Beginning balance at Apr. 30, 2020	901,631	$ 280	872,237	1,887	27,227
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		1,597,761
Issuance of common stock upon exercise of stock options	7,956	$ 2	7,954
Issuance of common stock upon release of restricted stock units (in shares)		147,023
Issuance of common stock for employee stock purchase plan (in shares)		605,924
Issuance of common stock for employee stock purchase plan	20,760	$ 1	20,759
Charitable donation of common stock	22,312		22,312
Stock-based compensation expense	59,279		59,279
Other comprehensive income (loss)	885			885
Net income	185,989				185,989
Ending balance (in shares) at Jul. 31, 2020		284,342,719
Ending balance at Jul. 31, 2020	1,198,812	$ 283	982,541	2,772	213,216
Beginning balance (in shares) at Jan. 31, 2021		293,549,223
Beginning balance at Jan. 31, 2021	$ 3,860,767	$ 292	3,187,168	839	672,468
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	1,593,193	1,593,193
Issuance of common stock upon exercise of stock options	$ 8,237	$ 2	8,235
Issuance of common stock upon release of restricted stock units (in shares)		1,182,958
Issuance of common stock upon release of restricted stock units	1	$ 1
Issuance of common stock for employee stock purchase plan (in shares)		701,949
Issuance of common stock for employee stock purchase plan	37,846	$ 1	37,845
Stock-based compensation expense	206,974		206,974
Other comprehensive income (loss)	(692)			(692)
Net income	544,615				544,615
Ending balance (in shares) at Jul. 31, 2021		297,027,323
Ending balance at Jul. 31, 2021	4,657,748	$ 296	3,440,222	147	1,217,083
Beginning balance (in shares) at Apr. 30, 2021		294,511,945
Beginning balance at Apr. 30, 2021	4,192,733	$ 293	3,292,241	200	899,999
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		841,507
Issuance of common stock upon exercise of stock options	4,761	$ 1	4,760
Issuance of common stock upon release of restricted stock units (in shares)		971,922
Issuance of common stock upon release of restricted stock units	1	$ 1
Issuance of common stock for employee stock purchase plan (in shares)		701,949
Issuance of common stock for employee stock purchase plan	37,846	$ 1	37,845
Stock-based compensation expense	105,376		105,376
Other comprehensive income (loss)	(53)			(53)
Net income	317,084				317,084
Ending balance (in shares) at Jul. 31, 2021		297,027,323
Ending balance at Jul. 31, 2021	$ 4,657,748	$ 296	$ 3,440,222	$ 147	$ 1,217,083