Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table presents the Company’s financial assets and liabilities measured at fair value on a recurring basis as of September 30, 2013 and December 31, 2012 (in thousands):

	SEPTEMBER 30, 2013
	TOTAL		LEVEL 1		LEVEL 2		LEVEL 3
Assets
Money market funds	$	28,660	$	28,660	$	—	$	—

	DECEMBER 31, 2012
	TOTAL		LEVEL 1		LEVEL 2		LEVEL 3
Assets
Money market funds	$	7,668	$	7,668	$	—	$	—
Liabilities
Common stock warrant liability	$	301	$	—	$	—	$	301
Preferred stock warrant liability		1,884		—		—		1,884
Convertible notes payable		41,860		—		—		41,860
Total liabilities at fair value	$	44,045	$	—	$	—	$	44,045

Reconciliation of Liabilities Measured At Fair Value Using Significant Unobservable Inputs (Level 3)

The following table provides a reconciliation of the beginning and ending balances for the common and preferred stock warrant liabilities measured at fair value using significant unobservable inputs (Level 3). The amounts included in the “Transfers out of Level 3” represent the beginning balance in the interim quarter during which it was transferred (in thousands):

	COMMON STOCK WARRANT LIABILITY
Fair value at December 31, 2012	$	301
Warrants issued		900
Change in fair value recorded in change in fair value of financial instruments		377
Transfers out of Level 3		(434	)
Reclassified to stockholders’ equity (deficit)		(1,144	)
Fair value at September 30, 2013	$	—

	PREFERRED STOCK WARRANT LIABILITY
Fair value at December 31, 2012	$	1,884
Change in fair value recorded in change in fair value of financial instruments		(823	)
Transfers out of Level 3		(140	)
Reclassified to stockholders’ equity (deficit)		(921	)
Fair value at September 30, 2013	$	—

The following table provides a reconciliation of the beginning and ending balances for the convertible notes measured at fair value using significant unobservable inputs (Level 3). The amounts included in the “Transfers out of Level 3” represent the beginning balance in the interim quarter during which it was transferred (in thousands):

Fair value at December 31, 2012	$	41,860
Convertible notes issued		9,069
Convertible notes cancelled		(1,360	)
Accrued interest		1,299
Change in fair valued recorded in change in fair value of financial instruments		(2,634	)
Transfers out of Level 3		(48,234	)
Fair value at September 30, 2013	$	—