Redeemable Convertible Preferred Stock - Allocation of Net Proceeds From Financing (Detail) - USD ($)		9 Months Ended
	Aug. 16, 2017	Sep. 30, 2017	Sep. 30, 2016
Allocation Of Net Proceeds From Redeemable Convertible Preferred Stock Financing [Line Items]
Common stock warrant liability	$ 3,498,632
Embedded derivative, redemption features	19,857
Initial carrying value of redeemable preferred stock	6,276,228
Net proceeds from redeemable preferred stock issuance	13,018,570	$ 13,018,570	$ 5,673,680
Series B Redeemable Convertible Preferred Stock [Member] | Fair Value, Inputs, Level 3 [Member]
Allocation Of Net Proceeds From Redeemable Convertible Preferred Stock Financing [Line Items]
Beneficial conversion feature	$ 3,223,853