Stockholders’ Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended						12 Months Ended
	Dec. 31, 2019	Jul. 31, 2019	Dec. 31, 2018	Apr. 30, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Accretion to redemption price of redeemable convertible preferred stock (less than for the three months ended June 30, 2019 and 2018)							$ 96	$ 162	$ 143
Issuance of redeemable convertible preferred stock, net of issuance costs (in shares)								12,655,000	11,774,000
Issuance of redeemable convertible preferred stock, net of issuance costs								$ 104,750	$ 52,346
Common stock, shares authorized (in shares)	900,000,000	900,000,000	99,250,000	99,250,000		80,000,000	900,000,000	99,250,000
Preferred stock, shares authorized (in shares)	100,000,000	100,000,000	0	58,615,488		45,960,013	100,000,000	0
Stock converted		$ 237,000
Preferred stock, shares issued (in shares)	0		0				0	0
Preferred stock, shares outstanding (in shares)	0		0				0	0
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001				$ 0.001	$ 0.001
Conversion trigger minimum Common Stock price per share (in dollars per share)	8.9180						$ 8.9180
Conversion trigger minimum cash proceeds in public offering							$ 50,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	0.001				$ 0.001	0.001
IPO
Class of Stock [Line Items]
Sale of stock (in shares)		14,590,050
Offering price (in dollars per share)		$ 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)		1,903,050
Secondary Offering - Shares From Existing Shareholders
Class of Stock [Line Items]
Offering price (in dollars per share)			$ 7.4672		$ 1.88			$ 7.4672	$ 1.88
Share based compensation			$ 2,300
Common Stock
Class of Stock [Line Items]
Stock converted (in shares)		58,615,488
Common Stock | Secondary Offering - Shares From Existing Shareholders
Class of Stock [Line Items]
Sale of stock (in shares)	2,777,327		2,138,302		605,345
Offering price (in dollars per share)	$ 27.00						27.00
Redeemable convertible preferred stock | Secondary Offering - Shares From Existing Shareholders
Class of Stock [Line Items]
Sale of stock (in shares)			57,945
Series A Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Dividend rate (in dollars per share)							0.081968
Conversion price (in dollars per share)	1.0246						1.0246
Series B Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Dividend rate (in dollars per share)							0.1824
Conversion price (in dollars per share)	2.2384						2.2384
Series C Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Dividend rate (in dollars per share)							0.2666
Conversion price (in dollars per share)	3.3318						3.3318
Series D Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Issuance of redeemable convertible preferred stock, net of issuance costs (in shares)						11,773,932
Issuance of redeemable convertible preferred stock, net of issuance costs						$ 52,500
Temporary equity issued during period, (in dollars per share)						$ 4.4590
Dividend rate (in dollars per share)						$ 0.3568	0.3568
Conversion price (in dollars per share)	4.4590						4.4590
Series E Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Issuance of redeemable convertible preferred stock, net of issuance costs (in shares)				12,655,477
Issuance of redeemable convertible preferred stock, net of issuance costs				$ 105,000
Temporary equity issued during period, (in dollars per share)				$ 8.2968
Dividend rate (in dollars per share)				$ 0.6638			0.6638
Conversion price (in dollars per share)	$ 8.2968						$ 8.2968