Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Differences Between United States Federal Income Tax Rate and Effective Income Tax Rate

The total income tax provision (benefit) differed from the amounts computed by applying the U.S. federal income tax rate of 35.0% to net income (loss) before income taxes as a result of the following:

	Year Ended December 31,
	2017		2016		2015
Statutory tax (benefit) expense	(35.0	)%	(35.0	)%	(35.0	)%
Increase (decrease) in taxes resulting from:
Stock-based compensation	—		0.2		0.1
Nondeductible expenses	0.2		0.4		0.2
Tax Cuts and Jobs Act impact	93.2		—		—
Valuation allowance	(58.4	)	34.4		34.7
	0.0	%	0.0	%	0.0	%

Deferred Tax Assets and Deferred Tax Liabilities

The tax effects of temporary differences that gave rise to significant portions of the deferred tax assets were as follows:

	As of December 31,
	2017			2016
	(In thousands)
Deferred tax asset:
Carrying values of partner companies and other holdings	$	69,751		$	95,134
Tax loss and credit carryforwards	58,138			82,775
Accrued expenses	766			1,183
Stock-based compensation	814			1,763
Other	967			1,310
	130,436			182,165
Valuation allowance	(130,436		)	(182,165		)
Net deferred tax asset	$	—		$	—

Carryforwards Expiration

As of December 31, 2017, the Company and its subsidiaries consolidated for tax purposes had federal net operating loss carryforwards of approximately $254.3 million. These carryforwards expire as follows:

	Total
	(In thousands)
2018	$	—
2019	—
2020	—
2021	3,728
2022 and thereafter	250,572
	$	254,300