Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value of Financial Instruments

Schedule of assets and liabilities measured at fair value on a recurring basis

As of December 31, 2012 (in thousands)	Level 1		Level 2		Level 3
Assets:
Cash equivalents — money market funds	$	25,668	$	—	$	—
Cash equivalents — certificates of deposit	—		480		—
Cash equivalents — corporate debt securities	—		5,017		—
Investments — certificates of deposit	—		240		—
Investments — commercial paper	—		12,465		—
Investments — corporate debt securities	—		59,533		—
Liabilities:
Derivative liability	$	—	$	—	$	196

As of September 30, 2013 (in thousands)	Level 1		Level 2		Level 3
Assets:
Cash equivalents — money market funds	$	94,962	$	—	$	—
Investments — certificates of deposit	—		960		—
Investments — commercial paper	—		34,487		—
Investments — corporate debt securities	—		41,587		—
Liabilities:
Derivative liability	$	—	$	—	$	231

Schedule of quantitative information associated with the fair value measurement of the Company's Level 3 inputs

	Fair Value as of September 30, 2013		Valuation Technique	Unobservable Input	Point Estimate
	(in thousands)
Derivative Liability	$	231	Probability-weighted	Estimated probability of Silver Creek qualified financing(s) prior to December 31, 2013	50	%

Schedule of fair value of the derivative liability categorized as Level 3 instruments

(in thousands)	Derivative Liability
Balance, December 31, 2012	$	196
Portion of convertible notes issued in February 2013 allocated to derivative	35
Balance, September 30, 2013	$	231

Schedule of quantitative information associated with the fair value measurement of the Company's non-recurring Level 3 inputs

	Fair Value as of September 30, 2013		Valuation Technique	Unobservable Input	Percentage
	(in thousands)
IPR&D asset	$	—	Income approach — Probability weighted discounted cash flow analysis	Discount rate	25.7	%