Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Tax Effects of Temporary Differences that Give Rise to Net Deferred Tax Assets

The following table sets forth the tax effects of temporary differences that give rise to significant portions of the Company’s net deferred tax assets (in thousands).  

	December 31,
	2016			2015			2014
Deferred tax assets:
Net operating loss carryforwards	$	133,514		$	123,647		$	115,870
Research and other credits		3,482			5,610			6,047
Other temporary differences		2,319			4,804			(2,478	)
Deferred tax assets - before valuation allowance		139,315			134,061			119,439
Valuation allowance		(139,315	)		(134,061	)		(119,439	)
Net deferred tax assets - after valuation allowance	$	-		$	-		$	-

Reconciling Items from Income Tax Computed at Statutory Federal Rate

The following table sets forth reconciling items from income tax computed at the statutory federal rate.  

	Year Ended December 31,
	2016			2015			2014
Federal income tax at statutory rate		35.0	%		35.0	%		35.0	%
State income taxes, net of federal benefits		2.9	%		5.4	%		4.5	%
Research and other credits		-5.8	%		-1.2	%		-1.3	%
Permanent deductions		-18.0	%		-4.0	%		-2.2	%
Valuation allowance		-14.1	%		-35.2	%		-36.0	%
Effective tax rate		0.0	%		0.0	%		0.0	%