Stockholders' Equity (Deficit) - Narrative (Details)	1 Months Ended		2 Months Ended	12 Months Ended
	Jan. 31, 2021 shares	Sep. 30, 2020 USD ($) shares	Mar. 15, 2021 shares	Dec. 31, 2020 USD ($) vote $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Oct. 05, 2020 shares	Dec. 31, 2017 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)				200,000,000	240,000,000		200,000,000
Dividends declared | $				$ 0
Number of votes for each share of common stock held | vote				1
Stock retired during period (shares)					414
Shares reserved for future issuance (in shares)				6,877,197	21,155,368
Options exercised, aggregate intrinsic value | $				$ 2,000,000.0	$ 200,000	$ 100,000
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares				$ 4.72	$ 1.66	$ 1.51		$ 1.52
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares				$ 4.72	$ 1.66
Options outstanding, aggregate intrinsic value | $				$ 188,000,000.0	$ 10,900,000
Options exercisable, aggregate intrinsic value | $				188,000,000.0	10,900,000
Options vested and expenses to vest, intrinsic value | $				$ 81,700,000	$ 7,600,000
Repurchase of early exercised common stock options (in shares)				10,000	9,147
Common stock, shares repurchased, less than | $				$ 100,000	$ 100,000
Aggregate exercise price of shares subject to repurchase | $				$ 600,000	$ 300,000
Options granted (in shares)				1,466,071	1,078,957	255,900
Fair value of stock options granted (in dollars per share) | $ / shares				$ 3.78	$ 1.79	$ 0.70
Stock-based compensation capitalized into inventory | $				$ 300,000	$ 0	$ 0
Unrecognized compensation costs | $				14,800,000
Fair value of shares vested | $				$ 1,900,000	$ 300,000	$ 400,000
Stock Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)				9,842,151
2000 Stock Plan | Directors, Employees And Consultants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)				0	0
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percentage of fair market value, greater than				100.00%
Award vesting period				4 years
Award expiration period, not more than				10 years
Shares subject to repurchase (in shares)				355,677	199,810
Weighted-average period for recognition of compensation costs				2 years 3 months 10 days
Options to purchase common stock | Share-based Payment Arrangement, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rate				25.00%
Options to purchase common stock | Share-based Payment Arrangement, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rate				25.00%
Options to purchase common stock | Share-based Payment Arrangement, Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rate				25.00%
Options to purchase common stock | Share-based Payment Arrangement, Tranche Four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rate				25.00%
Options to purchase common stock | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)			8,600
Options to purchase common stock | Over 10% Shareholder
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percentage of fair market value, greater than				110.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)		720,000		720,000	0
Purchase price of common stock, percentage of fair market value, greater than		85.00%
Payroll deduction rate, percentage of base compensation		15.00%
Maximum number of shares available per employee (in shares)		2,500
Maximum value of shares available per employee | $		$ 25,000
Shares issued in period (in shares)				0
Unrecognized compensation costs | $				$ 2,300,000
Weighted-average period for recognition of compensation costs				4 months 24 days
Employee Stock Purchase Plan | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares from automatic increase provision (in shares)	356,937