Equity - Narrative (Details) $ / shares in Units, $ in Thousands		1 Months Ended				2 Months Ended	11 Months Ended		12 Months Ended			13 Months Ended
	Oct. 31, 2020	Mar. 31, 2020 shares	Jun. 30, 2019 shares	Dec. 31, 2017 $ / shares shares	Jan. 31, 2016 shares	Jun. 30, 2020 USD ($)	Jan. 31, 2019 USD ($) shares	Nov. 30, 2018 private_placement	Jan. 31, 2021 USD ($) $ / shares shares	Jan. 31, 2020 USD ($) $ / shares shares	Jan. 31, 2019 USD ($) $ / shares shares	Apr. 30, 2020 USD ($)	Sep. 30, 2020 class vote $ / shares shares	Feb. 29, 2020 $ / shares	Jan. 31, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award
Preferred stock, shares authorized (in shares)									200,000,000	0			200,000,000
Preferred stock, par value (in dollars per share) | $ / shares									$ 0.0001	$ 0.0001			$ 0.0001
Common stock, number of classes of stock | class													2
Conversion, percent threshold									10.00%
Number of tender offers approved | private_placement								2
Number of shares issued (in shares)							6,000,000.0
Net proceeds | $							$ 60,000
Fair value of the shares tendered | $							$ 29,700
Excess of the fair value of common stock | $											$ 30,300
Common stock reserved for future issuances (shares)									112,494,580	251,269,209
Granted (per share) | $ / shares									$ 22.67	$ 4.41	$ 3.73
Intrinsic value of shares exercised | $									$ 2,000,000	$ 89,900	$ 29,300
Grant date fair value of vested shares | $									90,900	53,500	9,400
Proceeds from repayments of a nonrecourse promissory note | $									2,090	0	0
Share-based compensation expense | $									$ 301,441	$ 78,399	$ 52,738
Shares subject to repurchase (in shares)									245,633	2,104,331
Liabilities for common stock subject to repurchase | $									$ 1,200	$ 4,500
Compensation modification cost | $									2,700	$ 14,000		$ 16,700
Unrecognized share-based compensation expense | $									$ 1,100,000
Unrecognized share-based compensation expense recognition period (term)	3 years
ESPP
Share-based Compensation Arrangement by Share-based Payment Award
Common stock reserved for future issuances (shares)									5,700,000	0
Stock market discount									85.00%
Offering period									6 months
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)									4 years
Expiration period (years)									10 years
RSA | Share-based Payment Arrangement, Employee
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)					4 years
Shares authorized (shares)					1,609,778
Fair value of common stock, share price (in dollars per share) | $ / shares										$ 0.65
RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)									4 years
Unvested shares (shares)									9,348,557	0
Vested (shares)									36,436
Share-based compensation expense | $									$ 178,700
Cumulative share-based compensation expense | $									$ 55,500
The Plan | RSA
Share-based Compensation Arrangement by Share-based Payment Award
Unvested shares (shares)							920,380		0	16,700	920,380				392,210
Vested (shares)									16,700	920,380	421,830
Repurchased (in shares)										0
2020 Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Common stock reserved for future issuances (shares)									1,828,083	0
2012 Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Common stock reserved for future issuances (shares)									64,574,656	80,903,200
2012 Plan | RSA
Share-based Compensation Arrangement by Share-based Payment Award
Grant date fair value of shares other than options vested | $									$ 100	$ 6,700	$ 2,000
2012 Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award
Common stock reserved for future issuances (shares)									7,520,474	0
Out of the Plans | RSA
Share-based Compensation Arrangement by Share-based Payment Award
Unvested shares (shares)							1,652,446		741,911	1,603,562	1,652,446				2,054,890
Vested (shares)									861,651	442,222	402,444
Repurchased (in shares)			(268,297)							(268,297)
Out of the Plans | RSA | Private-Held Company
Share-based Compensation Arrangement by Share-based Payment Award
Issuance of common stock in connection with an acquisition (in shares)										661,635
Share-based compensation expense | $										$ 1,100
Service period										4 years
Out of the Plans | RSA | Privately-Held Company
Share-based Compensation Arrangement by Share-based Payment Award
Vested (shares)										215,031
Out of the Plans | RSA | Grant Date | Private-Held Company
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)										4 years
Out of the Plans | RSA | Promissory Notes
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)				5 years
Shares authorized (shares)				1,250,000
Shares issued (per share) | $ / shares				$ 1.59
Debt instrument, stated interest rate				2.11%
Proceeds from repayments of a nonrecourse promissory note | $						$ 2,100
Unvested shares (shares)									500,000
Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award
Common stock, shares authorized (in shares)									2,500,000,000	2,000			2,500,000,000
Votes per share (votes) | vote													1
Common stock, par value (in dollars per share) | $ / shares									$ 0.0001	$ 0.0001			$ 0.0001
Class A Common Stock | ESPP
Share-based Compensation Arrangement by Share-based Payment Award
Common stock reserved for future issuances (shares)													5,700,000
Class A Common Stock | 2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award
Common stock reserved for future issuances (shares)													34,100,000
Maximum common shares authorized to be outstanding (shares)													78,816,888
Class B Common Stock
Share-based Compensation Arrangement by Share-based Payment Award
Common stock, shares authorized (in shares)									355,000,000	312,000,000			355,000,000
Votes per share (votes) | vote													10
Common stock, par value (in dollars per share) | $ / shares									$ 0.0001	$ 0.0001			$ 0.0001
Shares issued (per share) | $ / shares														$ 38.77
Shares issued for common stock (shares)		8,600,000