Warrants - Additional Information (Detail) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended
	Mar. 30, 2019 shares	Aug. 31, 2015 $ / shares shares	Jul. 31, 2015 $ / shares shares	Mar. 31, 2019 USD ($) shares	Mar. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2013 $ / shares shares
Common Stock Warrants [Line Items]
Placement warrants not excercised and remained outstanding				2,818,576
(Gain) loss related to change in fair value | $				$ 3,120	$ (8,182)
2018 Direct Registered Offering | Common Stock
Common Stock Warrants [Line Items]
Warrants issued					1,418,116
Exercise price | $ / shares					$ 8.31
Common stock warrants, expiration date					Mar. 31, 2025
Proceed from private placement and equity issuances, gross | $					$ 59,100
Fair value of warrants upon issuance | $					$ 7,400
Warrants, fair value measurement inputs					7 years
Allocated portion of proceeds from issuance of stock and warrants | $					$ 6,600
2018 Direct Registered Offering | Common Stock | Expected Volatility
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs					0.625
2018 Direct Registered Offering | Common Stock | Risk-free Interest Rate
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs					0.028
2018 Direct Registered Offering | Common Stock | Expected Dividend Yield
Common Stock Warrants [Line Items]
Warrants, fair value measurement inputs					0.00
Equity Classified Common Stock Warrants
Common Stock Warrants [Line Items]
Warrants issued						128,231
Exercise price | $ / shares						$ 5.84
Common stock warrants, expiration date				Dec. 16, 2023
2015 Placement Equity Classified Common Stock Warrants | Insiders
Common Stock Warrants [Line Items]
Warrants issued		198,760	198,760
Exercise price | $ / shares		$ 5.00	$ 5.00
Warrant expiration period		5 years	5 years
Number of warrant exercised	159,010
Stock issued during period	92,487
Placement warrants not excercised and remained outstanding				39,750
2016 and 2017 Placement Warrants | Common Stock
Common Stock Warrants [Line Items]
(Gain) loss related to change in fair value | $				$ 3,000	$ (8,200)