Summary of Series B Convertible Preferred Stock and Accretion of Dividend (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stockholders Equity [Line Items]
Dividends earned on Series B preferred stock	$ 284	$ 270
Series B Convertible Preferred Stock
Stockholders Equity [Line Items]
Balance at beginning of period	22,969	21,875
Dividends earned on Series B preferred stock	284	270
Balance at end of period	$ 23,253	$ 22,145
Number of shares at beginning of period	5,742	5,469
Cumulative dividends on Series B convertible preferred stock	71	67
Number of shares at end of period	5,813	5,536