Equity Financing - Additional Information (Detail) - USD ($)		1 Months Ended			9 Months Ended
	Sep. 30, 2017	Jan. 31, 2017	Sep. 30, 2016	Aug. 31, 2016	Sep. 30, 2017	Sep. 30, 2016	Apr. 30, 2017
2016 Placement Warrants Liability
Subsidiary Sale Of Stock [Line Items]
Warrants to purchase common stock, shares			1,380,745	1,380,745		1,380,745
Warrant exercise price			$ 2.95	$ 2.95		$ 2.95
Proceed from private placement and equity issuances, gross			$ 13,800,000		$ 13,800,000
Warrant expiration period			7 years	7 years
2016 Placement Warrants Liability | Common Stock
Subsidiary Sale Of Stock [Line Items]
Private placement, common shares			4,602,506
2017 Placement Warrant
Subsidiary Sale Of Stock [Line Items]
Warrants to purchase common stock, shares		1,720,512
Warrant exercise price		$ 3.17
Proceed from private placement and equity issuances, gross		$ 26,100,000
Warrant exercisable date		Jul. 31, 2017
Warrant expiration date		Jan. 31, 2024
2017 Placement Warrant | Common Stock
Subsidiary Sale Of Stock [Line Items]
Private placement, common shares		8,602,589
At The Market Offering Program
Subsidiary Sale Of Stock [Line Items]
Compensation percentage pertaining to gross sales price per share sold					3.00%
Stock issued during period	0
Average market price per share	$ 6.10				$ 6.10
Aggregate gross proceeds from issuance of common stock	$ 40,100,000				$ 40,126,000	$ 0
At The Market Offering Program | Maximum
Subsidiary Sale Of Stock [Line Items]
Maximum aggregate offering price		$ 75,000,000					$ 100,000,000
Maximum common stock saleable value		$ 25,000,000					$ 25,000,000
At The Market Offering Program | Common Stock
Subsidiary Sale Of Stock [Line Items]
Stock issued during period					6,575,062