Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock and additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)
Beginning balance at Jan. 31, 2019		$ 744,907	$ (492,211)	$ (319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and other activity, net		46,911
Issuance of common stock for bonus settlement		2,809
Stock-based compensation		90,518
Equity component of convertible senior notes, net of issuance costs		217,347
Equity component of early extinguishment and conversion of convertible senior notes		(26,713)
Proceeds from hedges related to convertible senior notes		405,851
Payments for warrants related to convertible senior notes		(358,622)
Purchases of capped calls related to convertible senior notes		(74,094)
Other, net		(3)
Net loss	$ (158,441)		(158,441)
Other comprehensive income (loss)				454
Ending balance at Oct. 31, 2019	398,394	1,048,911	(650,652)	135
Beginning balance at Jul. 31, 2019		839,535	(587,157)	(1,653)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and other activity, net		9,430
Issuance of common stock for bonus settlement		0
Stock-based compensation		36,180
Equity component of convertible senior notes, net of issuance costs		217,347
Equity component of early extinguishment and conversion of convertible senior notes		(26,713)
Proceeds from hedges related to convertible senior notes		405,851
Payments for warrants related to convertible senior notes		(358,622)
Purchases of capped calls related to convertible senior notes		(74,094)
Other, net		(3)
Net loss	(63,495)		(63,495)
Other comprehensive income (loss)				1,788
Ending balance at Oct. 31, 2019	398,394	1,048,911	(650,652)	135
Beginning balance at Jan. 31, 2020	405,344	1,105,576	(701,124)	892
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and other activity, net		51,053
Issuance of common stock for bonus settlement		9,818
Stock-based compensation		140,895
Equity component of convertible senior notes, net of issuance costs		306,220
Equity component of early extinguishment and conversion of convertible senior notes		70,493
Proceeds from hedges related to convertible senior notes		195,046
Payments for warrants related to convertible senior notes		(175,399)
Purchases of capped calls related to convertible senior notes		(133,975)
Other, net
Net loss	(190,526)		(190,526)
Other comprehensive income (loss)				1,679
Ending balance at Oct. 31, 2020	680,648	1,569,727	(891,650)	2,571
Beginning balance at Jul. 31, 2020		1,498,562	(818,886)	5,521
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and other activity, net		8,299
Issuance of common stock for bonus settlement		0
Stock-based compensation		54,049
Equity component of convertible senior notes, net of issuance costs		(12)
Equity component of early extinguishment and conversion of convertible senior notes		8,829
Proceeds from hedges related to convertible senior notes		0
Payments for warrants related to convertible senior notes		0
Purchases of capped calls related to convertible senior notes		0
Other, net		0
Net loss	(72,764)		(72,764)
Other comprehensive income (loss)				(2,950)
Ending balance at Oct. 31, 2020	$ 680,648	$ 1,569,727	$ (891,650)	$ 2,571