Summary of Series B Preferred Stock and Accretion of Dividends (Detail) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) shares
Stockholders Equity [Line Items]
Cumulative dividends on Series B Preferred Stock	$ 833
Series B Preferred Stock
Stockholders Equity [Line Items]
Balance at December 31, 2017	12,000
Issuance of Series B Preferred Stock	8,000
Cumulative dividends on Series B Preferred Stock	833
Balance at December 31, 2018	$ 20,833
Balance at December 31, 2017, Shares | shares	3,000
Issuance of Series B Preferred stock, Shares | shares	2,000
Cumulative dividends on Series B Preferred Stock, Shares | shares	208
Balance at December 31, 2018, Shares | shares	5,208
Series B Preferred Stock | Tranche One
Stockholders Equity [Line Items]
Balance at December 31, 2017	$ 12,000
Cumulative dividends on Series B Preferred Stock	600
Balance at December 31, 2018	$ 12,600
Balance at December 31, 2017, Shares | shares	3,000
Cumulative dividends on Series B Preferred Stock, Shares | shares	150
Balance at December 31, 2018, Shares | shares	3,150
Series B Preferred Stock | Tranche Two
Stockholders Equity [Line Items]
Issuance of Series B Preferred Stock	$ 8,000
Cumulative dividends on Series B Preferred Stock	233
Balance at December 31, 2018	$ 8,233
Issuance of Series B Preferred stock, Shares | shares	2,000
Cumulative dividends on Series B Preferred Stock, Shares | shares	58
Balance at December 31, 2018, Shares | shares	2,058