Summary of Series B Preferred Stock and Accretion of Dividend (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Stockholders Equity [Line Items]
Cumulative dividends on Series B preferred stock	$ 262	$ 780
Series B Preferred Stock
Stockholders Equity [Line Items]
Balance at December 31, 2018		20,833
Cumulative dividends on Series B preferred stock		780
Balance at September 30, 2019	$ 21,613	$ 21,613
Balance at December 31, 2018, Shares		5,208
Cumulative dividends on Series B preferred stock, Shares		195
Balance at March 31, 2019, Shares	5,403	5,403
Series B Preferred Stock | Tranche One
Stockholders Equity [Line Items]
Balance at December 31, 2018		$ 12,600
Cumulative dividends on Series B preferred stock		473
Balance at September 30, 2019	$ 13,073	$ 13,073
Balance at December 31, 2018, Shares		3,150
Cumulative dividends on Series B preferred stock, Shares		118
Balance at March 31, 2019, Shares	3,268	3,268
Series B Preferred Stock | Tranche Two
Stockholders Equity [Line Items]
Balance at December 31, 2018		$ 8,233
Cumulative dividends on Series B preferred stock		307
Balance at September 30, 2019	$ 8,540	$ 8,540
Balance at December 31, 2018, Shares		2,058
Cumulative dividends on Series B preferred stock, Shares		77
Balance at March 31, 2019, Shares	2,135	2,135