Income Taxes (Tables)

12 Months Ended

Dec. 31, 2013

Income Tax Disclosure [Abstract]

Schedule Components of Loss Before Income Taxes

The components of loss before income taxes were as follows:

	Year ended December 31,
	2013			2012			2011
U.S.	$	(26,018	)	$	(23,700	)	$	(15,300	)
Foreign		697			30			(298	)
Total	$	(25,321	)	$	(23,670	)	$	(15,598	)

Net Deferred Tax Assets

The significant components of the Company’s deferred tax assets are comprised of the following:

	Year ended December 31,
	2013			2012
Deferred tax assets:
U.S. net operating loss carryforwards	$	11,010		$	24,044
Foreign net operating loss carryforwards		659			587
Tax credit carryforwards		3,638			1,910
Capitalized research and development expenses, net		1,837			2,334
Deferred revenue		21,830			267
Accruals and other		4,177			289
Total deferred tax assets		43,151			29,431
Fixed assets		(2,596	)		—
Less valuation allowance		(40,555	)		(29,431	)
Net deferred taxes	$	—		$	—

Reconciliation of Income Tax Expense Computed at the Statutory Federal Income Tax Rate to Income Taxes as Reflected in the Financial Statements

A reconciliation of income tax expense computed at the statutory federal income tax rate to income taxes as reflected in the financial statements is as follows:

	Year ended December 31,
	2013			2012			2011
Federal income tax expense at statutory rate		34.0	%		34.0	%		34.0	%
State income tax, net of federal benefit		4.5	%		4.4	%		5.0	%
Permanent differences		(0.6	%)		(0.8	%)		(1.3	%)
Research and development credit		6.0	%		0.8	%		3.4	%
Other		0.0	%		0.6	%		(0.6	%)
Change in valuation allowance		(43.9	%)		(39.0	%)		(40.5	%)
Effective income tax rate		0.0	%		0.0	%		0.0	%