Equity Financing - Additional Information (Detail) - USD ($)		1 Months Ended			6 Months Ended
	Jun. 30, 2017	Jan. 31, 2017	Sep. 30, 2016	Aug. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Apr. 30, 2017
Subsidiary Sale Of Stock [Line Items]
Proceed from private placement and equity issuances, gross					$ 65,600,000
2016 Placement Warrants Liability
Subsidiary Sale Of Stock [Line Items]
Sales of share common stock, per share			$ 2.95
Warrants to purchase common stock, shares			1,380,745	1,380,745
Warrant exercise price			$ 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 expiration period		7 years
Warrant exercisable period		6 months
2017 Placement Warrant | Directors and/or Officers
Subsidiary Sale Of Stock [Line Items]
Warrant exercise price		$ 3.17
2017 Placement Warrant | Common Stock
Subsidiary Sale Of Stock [Line Items]
Private placement, common shares		8,602,589
At The Market Offering Program [Member]
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	$ 39,500,000				$ 39,524,000	$ 0
At The Market Offering Program [Member] | 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 [Member] | Common Stock
Subsidiary Sale Of Stock [Line Items]
Stock issued during period					6,482,682