CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Additional paid-in capital Capped Call	Accumulated other comprehensive loss	Accumulated deficit
Cumulative-effect adjustment from adoption of ASU | Accounting Standards Update 2016-02						$ 7,241
Balance, beginning of period at Jan. 31, 2019		$ 149	$ 2,754,858		$ (2,506)	(1,232,044)
Vesting of restricted stock units		2
Issuance of common stock upon ESPP purchase		0
Stock-based compensation			246,076
Capitalized software development costs			0
Issuance of common stock upon exercise of options			554
Vesting of early exercised options	$ 0		0
Taxes paid related to net share settlement of equity awards			(117,693)
Issuance of common stock upon ESPP purchase			34,482
Equity component of convertible senior notes, net			0
Purchase of capped calls				$ 0
Partial repurchase of convertible senior notes			0
Unrealized gain (loss) from investments (net of tax)					1,042
Net change in cumulative translation adjustments	(2,020)				(2,020)
Net loss	(256,301)					(256,301)
Balance, end of period at Jul. 31, 2019	1,433,840	151	2,918,277		(3,484)	(1,481,104)
Cumulative-effect adjustment from adoption of ASU | Accounting Standards Update 2016-02						0
Balance, beginning of period at Apr. 30, 2019		150	2,809,273		(3,165)	(1,380,232)
Vesting of restricted stock units		1
Issuance of common stock upon ESPP purchase		0
Stock-based compensation			123,013
Capitalized software development costs			0
Issuance of common stock upon exercise of options			195
Vesting of early exercised options			0
Taxes paid related to net share settlement of equity awards			(48,686)
Issuance of common stock upon ESPP purchase			34,482
Equity component of convertible senior notes, net			0
Purchase of capped calls				0
Partial repurchase of convertible senior notes			0
Unrealized gain (loss) from investments (net of tax)					710
Net change in cumulative translation adjustments	(1,029)				(1,029)
Net loss	(100,872)					(100,872)
Balance, end of period at Jul. 31, 2019	1,433,840	151	2,918,277		(3,484)	(1,481,104)
Cumulative-effect adjustment from adoption of ASU | Accounting Standards Update 2016-02						0
Balance, beginning of period at Jan. 31, 2020	1,999,429	157	3,566,055		(5,312)	(1,561,471)
Vesting of restricted stock units		2
Issuance of common stock upon ESPP purchase		1
Stock-based compensation			313,691
Capitalized software development costs			3,850
Issuance of common stock upon exercise of options			2,670
Vesting of early exercised options	117		117
Taxes paid related to net share settlement of equity awards			(49,228)
Issuance of common stock upon ESPP purchase			44,214
Equity component of convertible senior notes, net			342,062
Purchase of capped calls				(137,379)
Partial repurchase of convertible senior notes			(283,629)
Unrealized gain (loss) from investments (net of tax)					686
Net change in cumulative translation adjustments	(104)				(104)
Net loss	(566,901)					(566,901)
Balance, end of period at Jul. 31, 2020	1,669,481	160	3,802,423		(4,730)	(2,128,372)
Cumulative-effect adjustment from adoption of ASU | Accounting Standards Update 2016-02						0
Balance, beginning of period at Apr. 30, 2020		158	3,678,895		(1,948)	(1,867,050)
Vesting of restricted stock units		1
Issuance of common stock upon ESPP purchase		1
Stock-based compensation			154,873
Capitalized software development costs			2,074
Issuance of common stock upon exercise of options			1,252
Vesting of early exercised options			61
Taxes paid related to net share settlement of equity awards			0
Issuance of common stock upon ESPP purchase			44,214
Equity component of convertible senior notes, net			342,062
Purchase of capped calls				$ (137,379)
Partial repurchase of convertible senior notes			(283,629)
Unrealized gain (loss) from investments (net of tax)					(1,999)
Net change in cumulative translation adjustments	(783)				(783)
Net loss	(261,322)					(261,322)
Balance, end of period at Jul. 31, 2020	$ 1,669,481	$ 160	$ 3,802,423		$ (4,730)	$ (2,128,372)