Description of Business and Basis of Presentation - Additional Information (Detail) - USD ($)	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accounting Policies [Line Items]
VIEs Operations	$ (6,876,000)		$ (4,982,000)		$ (12,666,000)	$ (9,200,000)
Net loss attributable to non-controlling interest	(205,000)				(307,000)
Accumulated deficit	(214,335,000)				(214,335,000)		$ (207,171,000)
Cash and cash equivalents	14,995,000				14,995,000		8,417,000
Short-term investments	600,000				600,000		16,915,000
Net (loss) income	(9,894,000)	$ 2,423,000	4,237,000	$ (12,612,000)	(7,471,000)	(8,375,000)	(28,900,000)
Net cash used in operations					(16,548,000)	(8,429,000)	(17,200,000)
Verdeca LLC [Member]
Accounting Policies [Line Items]
VIEs Operations	0		$ 0		0	$ 0
VIEs assets or liabilities	$ 0				$ 0		$ 0