Organization, Business, Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Not Considered for Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not considered for calculation of diluted net loss per share	1,476,719	1,721,882	1,476,719	1,721,882
Class X Preferred Stock (if-converted to common stock) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not considered for calculation of diluted net loss per share	587,445	816,851	587,445	816,851
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not considered for calculation of diluted net loss per share	477,639	477,639	477,639	477,639
Common Stock Options and Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not considered for calculation of diluted net loss per share	409,568	425,450	409,568	425,450
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not considered for calculation of diluted net loss per share	2,067	1,942	2,067	1,942