CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	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)		6,164,676
Issuance of common stock upon exercise of stock options	24,291	$ 6	24,285
Issuance of common stock upon release of restricted stock units (in shares)		443,836
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	185,398		185,398
Other comprehensive income (loss)	508			508
Net income	411,706				411,706
Ending balance (in shares) at Oct. 31, 2020		285,945,579
Ending balance at Oct. 31, 2020	1,499,918	$ 284	1,086,459	1,317	411,858
Beginning balance (in shares) at Jul. 31, 2020		284,342,719
Beginning balance at Jul. 31, 2020	1,198,812	$ 283	982,541	2,772	213,216
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		1,333,924
Issuance of common stock upon exercise of stock options	6,610	$ 1	6,609
Issuance of common stock upon release of restricted stock units (in shares)		268,936
Stock-based compensation expense	97,309		97,309
Other comprehensive income (loss)	(1,455)			(1,455)
Net income	198,642				198,642
Ending balance (in shares) at Oct. 31, 2020		285,945,579
Ending balance at Oct. 31, 2020	1,499,918	$ 284	1,086,459	1,317	411,858
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)	2,205,249	2,205,249
Issuance of common stock upon exercise of stock options	$ 11,362	$ 3	11,359
Issuance of common stock upon release of restricted stock units (in shares)		1,480,536
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	324,678		324,678
Other comprehensive income (loss)	(5,967)			(5,967)
Net income	884,998				884,998
Ending balance (in shares) at Oct. 31, 2021		297,936,957
Ending balance at Oct. 31, 2021	5,113,685	$ 297	3,561,050	(5,128)	1,557,466
Beginning balance (in shares) at Jul. 31, 2021		297,027,323
Beginning balance at Jul. 31, 2021	4,657,748	$ 296	3,440,222	147	1,217,083
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		612,056
Issuance of common stock upon exercise of stock options	3,125	$ 1	3,124
Issuance of common stock upon release of restricted stock units (in shares)		297,578
Issuance of common stock upon release of restricted stock units	0	$ 0
Stock-based compensation expense	117,704		117,704
Other comprehensive income (loss)	(5,275)			(5,275)
Net income	340,383				340,383
Ending balance (in shares) at Oct. 31, 2021		297,936,957
Ending balance at Oct. 31, 2021	$ 5,113,685	$ 297	$ 3,561,050	$ (5,128)	$ 1,557,466