Income Taxes - Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax asset:
Carrying values of partner companies and other holdings	$ 83,042	$ 68,557
Tax loss and credit carryforwards	84,493	76,766
Accrued expenses	1,391	1,484
Stock-based compensation	1,655	4,761
Other	1,369	1,353
Deferred tax assets, gross	171,950	152,921
Valuation allowance	(171,950)	(152,921)
Net deferred tax asset	$ 0	$ 0