Summary of Series B Convertible Preferred Stock and Accretion of Dividend (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Stockholders Equity [Line Items]
Dividends earned on Series B preferred stock	$ 286	$ 272	$ 570	$ 543
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			570	543
Balance at end of period	$ 23,539	$ 22,418	$ 23,539	$ 22,418
Number of shares at beginning of period			5,742	5,469
Cumulative dividends on Series B convertible preferred stock			143	135
Number of shares at end of period	5,885	5,604	5,885	5,604