Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss and tax credit carryforwards	$ 37,841	$ 37,899
Stock based compensation	641	648
Investment in affiliates	299	264
Other	18	14
Depreciation and amortization	20	37
Deferred tax assets gross	38,819	38,862
Less - valuation allowance	(27,500)	(38,780)
Net deferred tax assets	11,319	82
Deferred tax liabilities:
Goodwill amortization	(9)	(103)
Net deferred tax liabilities	(9)	(103)
Net deferred tax assets (liabilities)	$ 11,310
Net deferred tax assets (liabilities)		$ (21)