Convertible Preferred Stock and Stockholders' Equity - Summary of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) (Details) - USD ($)		3 Months Ended		6 Months Ended
	Apr. 02, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Class Of Stock [Line Items]
Balance, January 1, 2018				$ (39,454,051)
Balance, January 1, 2018				137,762,160
Conversion of convertible preferred stock into common stock upon initial public offering				137,762,160
Convertible preferred shares converted to common stock	24,168,656
Sale of common stock in initial public offering				150,843,215
Vesting of common stock from option exercise				5,750
Issuance of common stock from option exercise				$ 85,301
Issuance of common stock from option exercise, Shares				53,884
Stock-based compensation				$ 949,192
Comprehensive gain		$ 37,519		24,662
Net loss		(12,894,236)	$ (6,002,754)	(23,417,798)	$ (11,557,547)
Balance, June 30, 2018		226,798,431		$ 226,798,431
Convertible Preferred Stock
Class Of Stock [Line Items]
Balance, Shares, January 1, 2018				127,199,705
Balance, January 1, 2018				$ 137,762,160
Conversion of convertible preferred stock into common stock upon initial public offering, Shares				(127,199,705)
Conversion of convertible preferred stock into common stock upon initial public offering				$ (137,762,160)
Common Stock
Class Of Stock [Line Items]
Balance, January 1, 2018				$ 264
Balance, Shares, January 1, 2018				2,637,011
Conversion of convertible preferred stock into common stock upon initial public offering				$ 2,417
Convertible preferred shares converted to common stock				24,168,656
Sale of common stock in initial public offering				$ 1,035
Shares issued and sold				10,350,000
Vesting of common stock from option exercise				$ 6
Vesting of common stock from option exercise, Shares				61,501
Issuance of common stock from option exercise				$ 4
Issuance of common stock from option exercise, Shares				37,734
Balance, June 30, 2018		$ 3,726		$ 3,726
Balance, Shares, June 30, 2018		37,254,902		37,254,902
Additional Paid-in Capital
Class Of Stock [Line Items]
Balance, January 1, 2018				$ 799,859
Conversion of convertible preferred stock into common stock upon initial public offering				137,759,743
Sale of common stock in initial public offering				150,842,180
Vesting of common stock from option exercise				5,744
Issuance of common stock from option exercise				85,297
Stock-based compensation				949,192
Balance, June 30, 2018		$ 290,442,015		290,442,015
Accumulated Other Comprehensive Loss
Class Of Stock [Line Items]
Balance, January 1, 2018				(73,308)
Comprehensive gain				24,662
Balance, June 30, 2018		(48,646)		(48,646)
Accumulated Deficit
Class Of Stock [Line Items]
Balance, January 1, 2018				(40,180,866)
Net loss				(23,417,798)
Balance, June 30, 2018		$ (63,598,664)		$ (63,598,664)