Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value Disclosures [Abstract]

Schedule of fair value of financial assets and liabilities measured at fair value and classification by level of input

	Fair Value Measurements as of
	September 30, 2015
(in thousands)	Level 1		Level 2		Level 3		Total
Investments:
Money market funds	$	7,396	$	—	$	—	$	7,396
Total assets measured at fair value	$	7,396	$		$	—	$	7,396
Financing derivative	$	—	$	—	$	341	$	341
Total liabilities measured at fair value	$	—	$	—	$	341	$	341

	Fair Value Measurements as of
	December 31, 2014
(in thousands)	Level 1		Level 2		Level 3		Total
Investments:
Money market funds	$	9,663	$	—	$	—	$	9,663
Federal agency securities		—		13,770		—		13,770
Commercial paper		—		1,500		—		1,500
Corporate debt securities		—		14,520		—		14,520
Total assets measured at fair value	$	9,663	$	29,790	$	—	$	39,453
Financing derivative	$	—	$	—	$	89	$	89
Total liabilities measured at fair value	$	—	$	—	$	89	$	89

Schedule of changes in financial instruments measured at fair value using Level 3 inputs

	Fair Value Measurements of Level 3 Liabilities
	(in thousands)
Balance as of December 31, 2014	$	89
Loss on re-measurement of the financing derivative liability		3
Balance as of March 31, 2015		92
Loss on re-measurement of the financing derivative liability		135
Balance as of June 30, 2015		227
Loss on re-measurement of the financing derivative liability		114
Balance as of September 30, 2015	$	341