Summary of Series B Convertible Preferred Stock and Accretion of Dividend (Detail) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stockholders Equity [Line Items]
Dividends earned on Series B preferred stock	$ 1,094	$ 1,042
Series B Convertible Preferred Stock
Stockholders Equity [Line Items]
Balance at beginning of period	21,875	20,833
Dividends earned on Series B preferred stock	1,094	1,042
Balance at end of period	$ 22,969	$ 21,875
Number of shares at beginning of period	5,469	5,208
Cumulative dividends on Series B convertible preferred stock	273	261
Number of shares at end of period	5,742	5,469