Earnings Per Common Share ("EPS") - Components of Basic and Diluted EPS Computations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
EPS — basic and diluted:
Net loss (numerator)	$ (4,426)	$ (35,523)	$ (12,916)	$ (11,255)	$ (10,252)	$ (9,322)	$ (52,865)	$ (30,829)
Weighted average common shares (denominator)	249,910			229,668			248,624	218,559
Net loss per share	$ (0.02)			$ (0.05)			$ (0.21)	$ (0.14)