Income Taxes (Tables)

12 Months Ended

Dec. 31, 2012

Income Taxes

Schedule of reconciliation of the Company's effective tax rate to the statutory federal income tax rate

	Years ended December 31,
	2010			2011			2012
Federal statutory rate		35.0	%		35.0	%		35.0	%
State taxes, net of Federal benefit		4.6			4.2			4.5
Permanent differences		(2.6	)		(0.4	)		(0.2	)
Stock compensation		(2.9	)		(1.2	)		(0.3	)
Change in valuation allowance		(39.2	)		(36.3	)		(35.5	)
Tax credits		5.1			3.9			1.1
Foreign rate differentials		—			(4.4	)		(4.1	)
Other		—			(0.8	)		(0.5	)
		—	%		—	%		—	%

Schedule of temporary differences that give rise to significant net deferred tax assets

(in thousands)	2011			2012
Deferred tax assets
Net operating losses	$	40,633		$	77,806
Capitalized research and development expenses		47,640			40,083
Credit carryforwards		13,380			14,398
Depreciation		2,337			2,931
Deferred compensation		4,450			5,068
Deferred revenues		26,462			29,936
Accrued expenses		676			1,184
Other		922			1,934
Total gross deferred tax asset		136,500			173,340
Intangible assets		(3,817	)		(3,689	)
Valuation allowance		(132,683	)		(169,651	)
Net deferred taxes	$	—		$	—

Schedule of changes in the valuation allowance

(in thousands)	Balance at beginning of period		Additions		Deductions		Balance at end of period
December 31, 2010	$	81,420		22,461		—	$	103,881
December 31, 2011	$	103,881		28,802		—	$	132,683
December 31, 2012	$	132,683		36,968		—	$	169,651