Income Taxes - Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax asset:
Carrying values of partner companies and other holdings	$ 60,951	$ 69,751
Tax loss and credit carryforwards	62,901	58,138
Disallowed interest carryforwards	3,831	0
Credit facility repayment feature	1,312	0
Accrued expenses	675	766
Stock-based compensation	550	814
Other	1,034	967
Deferred tax assets, gross	131,254	130,436
Valuation allowance	(131,254)	(130,436)
Net deferred tax asset	$ 0	$ 0