Summary of Series B Convertible Preferred Stock and Accretion of Dividend (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stockholders Equity [Line Items]
Cumulative dividends on Series B convertible preferred stock	$ 270	$ 258
Series B convertible preferred stock
Stockholders Equity [Line Items]
Balance as of December 31, 2019	21,875
Cumulative dividends on Series B convertible preferred stock	270
Balance as of March 31, 2020	$ 22,145
Balance as of December 31, 2019, Shares	5,469
Cumulative dividends on Series B convertible preferred stock	67
Balance as of March 31, 2020, Shares	5,536
Series B convertible preferred stock | Tranche One
Stockholders Equity [Line Items]
Balance as of December 31, 2019	$ 13,230
Cumulative dividends on Series B convertible preferred stock	165
Balance as of March 31, 2020	$ 13,395
Balance as of December 31, 2019, Shares	3,308
Cumulative dividends on Series B convertible preferred stock	41
Balance as of March 31, 2020, Shares	3,349
Series B convertible preferred stock | Tranche two
Stockholders Equity [Line Items]
Balance as of December 31, 2019	$ 8,645
Cumulative dividends on Series B convertible preferred stock	105
Balance as of March 31, 2020	$ 8,750
Balance as of December 31, 2019, Shares	2,161
Cumulative dividends on Series B convertible preferred stock	26
Balance as of March 31, 2020, Shares	2,187