Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2014

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value on a Recurring Basis

Our assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability.

	As of September 30, 2014								As of December 31, 2013
Assets and Liabilities	Quoted Prices In Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of September 30, 2014		Quoted Prices In Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance at December 31, 2013
Assets:
Money market funds	$	59,862	$	—	$	—	$	59,862	$	30,325	$	—	$	—	$	30,325
Total assets at fair value	$	59,862	$	—	$	—	$	59,862	$	30,325	$	—	$	—	$	30,325
Liabilities:
Warrant liability	$	—	$	—	$	1	$	1	$	—	$	—	$	19	$	19
Total liabilities at fair value	$	—	$	—	$	1	$	1	$	—	$	—	$	19	$	19

Change in Fair Value Measurement Using Significant Unobservable Inputs (Level 3)

The change in the fair value measurement using significant unobservable inputs (Level 3) is summarized below (in thousands):

Balance at December 31, 2013	$	19
Change in fair value recorded as interest income		(69	)
Change in fair value recorded as interest expense		51
Balance at September 30, 2014	$	1