Organization and Description of Business - Narrative (Details) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Jun. 27, 2019	Jul. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 shares
Class of Stock [Line Items]
Redeemable convertible preferred stock, shares outstanding (in shares) | shares		58,615,488	0	58,615,000	45,960,000	34,186,000
Stock converted		$ 237,000
Accumulated deficit			$ (164,198)	$ (113,613)
Net loss			(55,270)	(33,382)	$ (16,858)
Net cash used in operating activities			(59,396)	(33,040)	(15,916)
Proceeds from issuance of redeemable convertible preferred stock			$ 0	$ 104,750	$ 52,346
IPO
Class of Stock [Line Items]
Sale of stock (in shares) | shares		14,590,050
Offering price (in dollars per share) | $ / shares		$ 28.00
Net proceeds from sale of stock		$ 377,500
Underwriting discounts and commissions		28,600
Offering expenses		$ 2,400
Underwriters' Option
Class of Stock [Line Items]
Sale of stock (in shares) | shares		1,903,050
Common Stock
Class of Stock [Line Items]
Stock converted (in shares) | shares		58,615,488
Reverse stock split conversion ratio	0.5
Redeemable convertible preferred stock
Class of Stock [Line Items]
Reverse stock split conversion ratio	0.5
Additional Paid-in Capital
Class of Stock [Line Items]
Stock converted		$ 236,900
Common Stock
Class of Stock [Line Items]
Stock converted (in shares) | shares			58,615,000
Stock converted		$ 100