Loss Per Common Share - Computation of Basic and Diluted Net Loss Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net loss	$ (13,279)	$ (19,452)
Adjustments for basic net loss per common share:
Dividend accrued on redeemable preferred stock	(9,511)	(8,307)
Dividend requirements	(75)	(75)
Net loss attributable to common stockholders	$ (23,376)	$ (28,338)
Denominator:
Denominator for basic and dilutive net loss per common share - adjusted weighted-average shares	28,343,693	28,176,205
Basic and dilutive net loss per common share	$ (0.82)	$ (1.01)
Series E Redeemable Preferred Stock [Member]
Adjustments for basic net loss per common share:
Dividend accrued on redeemable preferred stock	$ (9,511)	$ (8,307)
Accretion of redeemable preferred stock	(511)	(504)
Series B Preferred Stock [Member]
Adjustments for basic net loss per common share:
Dividend requirements	(60)	(60)
Series D Preferred Stock [Member]
Adjustments for basic net loss per common share:
Dividend requirements	$ (15)	$ (15)