Income Taxes (Tables)

12 Months Ended

Dec. 31, 2013

Income Taxes

Schedule of reconciliation of the statutory U.S. federal income tax rate to the entity's effective income tax rate

The reconciliation of the statutory U.S. federal income tax rate to our effective income tax rate is as follows:

	Years Ended December 31,
	2013			2012			2011
Statutory U.S. federal tax rate		(34.0	)%		(34.0	)%		(34.0	)%
State taxes, net of federal benefit		2.4	%		4.2	%		(3.4	)%
Equity-based compensation expense		9.4	%		42.4	%		2.4	%
Permanent items, net		5.3	%		1.2	%		0.4	%
Tax credits		0.5	%		0.8	%		(1.6	)%
Valuation allowance		16.4	%		(19.5	)%		34.7	%
Total tax (benefit) expense		0.0	%		(4.9	)%		(1.5	)%

Schedule of components of the entity's deferred tax assets and liabilities

The components of our deferred tax assets and liabilities are as follows (in thousands):

	December 31,
	2013			2012
Assets
Net operating loss carryforwards	$	85,269		$	75,740
Tax credit carryforwards		12,396			12,403
Deferred revenue		20,368			22,315
Equity-based compensation expense		4,176			3,681
Capitalized research & development		39,214			45,137
Intangibles		680
Other		4,371			4,239
Property and Equipment Depreciation		—			1,393
Liabilities
Property, Plant, and Equipment Depreciation		(58	)		—
		166,416			164,908
Valuation allowance		(166,416	)		(164,908	)
Net deferred taxes	$	—		$	—