Shareholders' Equity - Additional Information (Detail)	12 Months Ended		41 Months Ended
	Dec. 31, 2019 USD ($) Vote $ / shares shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2019 USD ($) Vote $ / shares shares	Jul. 28, 2016 USD ($)
Stockholders Equity Note [Line Items]
Common stock votes per share | Vote	1		1
Preferred stock, shares authorized | shares	5,000	5,000	5,000
ATM Program
Stockholders Equity Note [Line Items]
Proceeds from sale of common stock under ATM program	$ 4,606,000	$ 2,849,000
ATM Program | Cowen and Company LLC
Stockholders Equity Note [Line Items]
Aggregate offering price authorized				$ 75,000,000
Proceeds from sale of common stock under ATM program gross	4,713,000		$ 54,240,000
Proceeds from sale of common stock under ATM program	4,607,000		53,019,000
Commissions paid	$ 106,000		$ 1,220,000
ATM Program | Common Stock | Cowen and Company LLC
Stockholders Equity Note [Line Items]
Shares sold under ATM program | shares	1,250,000		4,955,936
Average price per share | $ / shares	$ 3.77		$ 10.94