Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Tax Disclosure [Abstract]

Reconciliation of Expected Income Tax Benefit

A reconciliation of the expected income tax benefit computed using the federal statutory income tax rate to the Company’s effective income tax rate is as follows for the years ended December 31, 2015, 2014 and 2013:

	December 31, 2015			December 31, 2014			December 31, 2013
Income tax computed at federal statutory tax rate		34.0	%		34.0	%		34.0	%
State taxes, net of federal benefit		5.3	%		5.3	%		5.1	%
Research and development credits		2.0	%		2.6	%		2.0	%
Other permanent differences		(2.0	)%		(0.8	)%		(0.9	)%
Foreign rate differential		(0.1	)%		0.0	%		(0.2	)%
Permanent difference – estimated settlement liability		(9.1	)%		0.0	%		0.0	%
Other		(3.8	)%		(5.7	)%		(0.5	)%
Change in valuation allowance		(26.3	)%		(35.4	)%		(39.5	)%
Total		0.0	%		0.0	%		0.0	%

Company Net Deferred Tax Assets

The Company’s net deferred tax assets as of December 31, 2015, 2014 and 2013 are as follows:

	December 31, 2015			December 31, 2014			December 31, 2013
NOL carryforwards	$	170,200		$	162,248		$	134,023
Research and development credits		12,721			12,721			11,357
Deferred revenue		1,451			302			7,224
Other temporary differences		5,935			11,135			15,158
Valuation allowance		(190,307	)		(186,406	)		(167,762	)
Total		—			—			—

Reconciliation of Gross Uncertain Tax Positions

The following is a reconciliation of the Company’s gross uncertain tax positions at December 31, 2015, 2014 and 2013:

	Year ended December 31,		Year ended December 31,			Year ended December 31,
	2015		2014			2013
		(in thousands)
Amount established upon adoption	$	1,200	$	1,200	$	1,200
Additions for current year tax positions		—		—		—
Additions for prior year tax positions		—		—		—
Reductions of prior year tax positions		—		—		—
Balance as of end of year	$	1,200	$	1,200	$	1,200