Financings - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended	12 Months Ended
	Mar. 10, 2020	Feb. 05, 2020	Sep. 12, 2019	Nov. 11, 2018	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Apr. 26, 2006
Class of Stock [Line Items]
Stock issued during period						2,814,673
Sale of stock consideration received on transaction						$ 88,661
Common stock, par value				$ 0.001		$ 0.001	$ 0.001	$ 0.001
Gross proceeds received						$ 13,016	$ 6,085
Class of warrant or right, number of securities called by warrants or rights				18,939,394
Warrant Exercise Price per share				$ 2.64
Proceeds from private placement			$ 52,500
Non-cash inducement warrant expense					$ (60,751)		$ 60,751
At The Market Offering [Member]
Class of Stock [Line Items]
Stock issued during period						2,814,673	1,271,274
Sale of stock consideration received on transaction						$ 13,000	$ 6,100
Private Placement [Member]
Class of Stock [Line Items]
Class of warrant or right, number of securities called by warrants or rights			17,803,031			18,939,394
Warrant Exercise Price per share			$ 3.01			$ 3.01
Placement agent fees and other expenses			$ 1,100
Private Placement [Member] | New Warrants [Member]
Class of Stock [Line Items]
Class of warrant or right, number of securities called by warrants or rights			17,803,031
Warrant Exercise Price per share			$ 7.00
Non-cash inducement warrant expense			$ 60,800			$ 60,800
Securities Purchase Agreement [Member]
Class of Stock [Line Items]
Stock issued during period				18,939,394
Common stock, par value				$ 0.001
par value per share				$ 2.64
Gross proceeds received				$ 47,100		47,100
Underwriting Agreement [Member]
Class of Stock [Line Items]
Stock issued during period		27,826,086					1,271,274
Issuance & sale of common stock in public offering price per share		$ 3.25
Sale of stock consideration received on transaction		$ 84,800				$ 13,000	$ 6,100
par value per share		$ 3.055
Underwriting Agreement [Member] | Maximum [Member]
Class of Stock [Line Items]
Stock issued during period		4,173,912
par value per share		$ 3.055
Underwriting Agreement [Member] | Stock Option [Member]
Class of Stock [Line Items]
Sale of stock consideration received on transaction	$ 3,900
Stock issued during period	1,284,025