Loss Per Common Share - Computation of Basic and Diluted Net Loss Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net loss	$ (365)	$ (19,452)	$ 6,631	$ (11,540)	$ (19,817)	$ (4,909)
Adjustments for basic net loss per common share:
Dividend accrued on redeemable preferred stock	(8,689)	$ (8,307)	(7,589)	$ (7,256)
Dividend requirements	(75)		(75)		(150)	(150)
Net loss attributable to common stockholders	$ (9,634)		$ (1,530)		$ (37,972)	$ (20,897)
Denominator:
Denominator for basic and dilutive net loss per common share - adjusted weighted-average shares	28,198,963		28,050,848		28,187,584	28,004,936
Basic and dilutive net loss per common share	$ (0.34)		$ (0.05)		$ (1.35)	$ (0.75)
Series E Redeemable Preferred Stock [Member]
Adjustments for basic net loss per common share:
Dividend accrued on redeemable preferred stock	$ (8,689)		$ (7,589)		$ (16,996)	$ (14,845)
Accretion of redeemable preferred stock	(505)		(497)		(1,009)	(993)
Series B Preferred Stock [Member]
Adjustments for basic net loss per common share:
Dividend requirements	(60)		(60)		(120)	(120)
Series D Preferred Stock [Member]
Adjustments for basic net loss per common share:
Dividend requirements	$ (15)		$ (15)		$ (30)	$ (30)