Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended		6 Months Ended
	Apr. 02, 2019	Jun. 30, 2020	Jul. 31, 2019	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Discounts, commissions and offering expenses				$ 1,186	$ 28
Aggregate offering price of common stock shares issued				11,915
Cash, cash equivalents and investments		$ 18,880		18,880		$ 18,880
Accumulated deficit		$ (209,273)		$ (209,273)		$ (209,273)	$ (198,135)
Stock market bidding requirements, description						On July 12, 2019, the Company received a deficiency letter from the Listing Qualifications Department of the Nasdaq Stock Market notifying the Company that, for the last 30 consecutive business days, the bid price for the Company’s common stock had closed below the minimum $1.00 per share requirement for continued inclusion on the Nasdaq Global Market (the “Bid Price Rule”). On December 20, 2019, the Company applied to transfer the listing of its stock from the Nasdaq Global Market to the Nasdaq Capital Market.
Minimum closing bid requirement, price per share						$ 1.00
Stock market effective bidding requirements, description						On December 27, 2019, Nasdaq approved the Company’s transfer application. This transfer became effective at the opening of business on December 30, 2019. On June 11, 2020, after the Company’s common stock had a closing price bid of at least $1.00 for 10 consecutive trading days, Nasdaq provided written notification to the Company that it had regained compliance with the Bid Price Rule and that Nasdaq considered the matter closed.
Common Stock [Member]
Class of Stock [Line Items]
Stock issued during period, shares				11,425,118
Aggregate offering price of common stock shares issued				$ 11
Sales Agreement [Member] | JonesTrading [Member]
Class of Stock [Line Items]
Discounts, commissions and offering expenses						$ 24
Aggregate number of common stock shares issued and sold						1,263,059
Gross proceeds from common stock shares issued and sold						$ 762
Sales Agreement [Member] | JonesTrading [Member] | Maximum [Member]
Class of Stock [Line Items]
Aggregate offering price of common stock shares issued			$ 13,265
Underwritten Public Offering [Member]
Class of Stock [Line Items]
Stock issued during period, shares		10,162,059
Additional shares of common stock issued upon partial exercise of option		1,071,149
Shares issued, price per share		$ 1.10		$ 1.10		$ 1.10
Gross proceeds from issuance of common stock		$ 11,178
Discounts, commissions and offering expenses		$ 932
Private Placement [Member]
Class of Stock [Line Items]
Discounts, commissions and offering expenses	$ 2,175
Aggregate gross proceeds from private placement	$ 26,000
Private Placement [Member] | Stock Units [Member] | Purchase Agreement One [Member]
Class of Stock [Line Items]
Shares issued, price per share	$ 2.01
Aggregate number of common stock shares issued and sold	11,838,582
Private Placement [Member] | Stock Units [Member] | Purchase Agreement Two [Member]
Class of Stock [Line Items]
Shares issued, price per share	$ 2.01
Aggregate number of common stock shares issued and sold	1,096,741
Private Placement [Member] | Common Warrants [Member] | Purchase Agreement One [Member]
Class of Stock [Line Items]
Aggregate shares purchase for warrants	11,838,582
Warrants exercisable, exercise price	$ 2.00
Warrants and rights outstanding, term	5 years
Private Placement [Member] | Common Stock [Member]
Class of Stock [Line Items]
Outstanding pre-funded warrants exercised			1,096,741
Private Placement [Member] | Common Stock [Member] | Purchase Agreement One [Member]
Class of Stock [Line Items]
Stock repurchase program, number of shares to be purchased	11,838,582
Private Placement [Member] | Common Stock [Member] | Purchase Agreement Two [Member]
Class of Stock [Line Items]
Stock repurchase program, number of shares to be purchased	1,096,741
Private Placement [Member] | Pre-funded Warrants [Member] | Purchase Agreement Two [Member]
Class of Stock [Line Items]
Aggregate shares purchase for warrants	1,096,741
Warrants exercisable, exercise price	$ 0.01