Stockholders’ Equity (Deficit) and Convertible Preferred Stock (Details) - $ / shares	May 06, 2019	Sep. 28, 2019	Aug. 05, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock, authorized (in shares)	500,000,000	500,000,000				58,669,600
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001				$ 0.0001
Convertible preferred stock, authorized (in shares)						43,882,867
Convertible preferred stock, par value (in shares)						$ 0.0001
Common stock, issued (in shares)		60,565,840				6,951,350
Common stock, outstanding (in shares)		60,565,840				6,951,350
Convertible preferred stock, outstanding (in shares)		0		0	41,562,111	41,562,111	39,486,895	39,486,895	39,474,156	39,361,211
Series A
Class of Stock [Line Items]
Convertible preferred stock, authorized (in shares)		0				3,333,500
Convertible preferred stock, par value (in shares)		$ 0.0001				$ 0.0001
Convertible preferred stock, issued (in shares)		0				3,333,500
Convertible preferred stock, outstanding (in shares)		0				3,333,500
Series B
Class of Stock [Line Items]
Convertible preferred stock, authorized (in shares)		0				4,802,260
Convertible preferred stock, par value (in shares)		$ 0.0001				$ 0.0001
Convertible preferred stock, issued (in shares)		0				4,680,565
Convertible preferred stock, outstanding (in shares)		0				4,680,565
Series C
Class of Stock [Line Items]
Convertible preferred stock, authorized (in shares)		0				8,076,643
Convertible preferred stock, par value (in shares)		$ 0.0001				$ 0.0001
Convertible preferred stock, issued (in shares)		0				8,076,636
Convertible preferred stock, outstanding (in shares)		0				8,076,636
Series D
Class of Stock [Line Items]
Convertible preferred stock, authorized (in shares)		0				8,713,207
Convertible preferred stock, par value (in shares)		$ 0.0001				$ 0.0001
Convertible preferred stock, issued (in shares)		0				8,713,201
Convertible preferred stock, outstanding (in shares)		0				8,713,201
Series E
Class of Stock [Line Items]
Convertible preferred stock, authorized (in shares)		0				4,740,531
Convertible preferred stock, par value (in shares)		$ 0.0001				$ 0.0001
Convertible preferred stock, issued (in shares)		0				4,701,449
Convertible preferred stock, outstanding (in shares)		0				4,701,449
Series F
Class of Stock [Line Items]
Convertible preferred stock, authorized (in shares)		0				4,866,776
Convertible preferred stock, par value (in shares)		$ 0.0001				$ 0.0001
Convertible preferred stock, issued (in shares)		0				4,866,758
Convertible preferred stock, outstanding (in shares)		0				4,866,758
Series G
Class of Stock [Line Items]
Convertible preferred stock, authorized (in shares)		0				5,140,257
Convertible preferred stock, par value (in shares)		$ 0.0001				$ 0.0001
Convertible preferred stock, issued (in shares)		0				5,114,786
Convertible preferred stock, outstanding (in shares)		0				5,114,786
Series H
Class of Stock [Line Items]
Convertible preferred stock, authorized (in shares)		0				4,209,693
Convertible preferred stock, par value (in shares)		$ 0.0001				$ 0.0001
Convertible preferred stock, issued (in shares)		0				2,075,216
Convertible preferred stock, outstanding (in shares)		0				2,075,216
IPO
Class of Stock [Line Items]
Number of common stock shares converted	41,562,111
Number of shares issued for each share of convertible preferred stock converted (in shares)	1
Convertible preferred stock, authorized (in shares)	500,000
Convertible preferred stock, par value (in shares)	$ 0.0001
Over-allotment option
Class of Stock [Line Items]
Selling stockholders sold (in shares)			250,000