Fair value financial measurements (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2015

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Schedule of Fair Value of Financial Liabilities

The following table sets forth the fair value of the Company’s financial liabilities by level within the fair value hierarchy (in thousands):

	At June 30, 2015
	Level 1		Level 2		Level 3		Total
	(Unaudited)
Convertible preferred stock warrant liability	$	—	$	—	$	87	$	87

	At December 31, 2014
	Level 1		Level 2		Level 3		Total
	(Unaudited)
Convertible preferred stock warrant liability	$	—	$	—	$	138	$	138

The following table sets forth the fair value of the Company’s financial liabilities by level within the fair value hierarchy (in thousands):

	December 31, 2013
	Fair Value		Level 1		Level 2		Level 3
Convertible preferred stock warrant liability	$	158	$	—	$	—	$	158

	December 31, 2013
	Fair Value		Level 1		Level 2		Level 3
Convertible preferred stock warrant liability	$	138	$	—	$	—	$	138

Summary of Changes in Fair Value of Level 3 Financial Liabilities

The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands):

	Six Months Ended June 30, 2015
	(Unaudited)
Fair value, beginning of period	$	138
Change in fair value of Level 3 financial liabilities		(51	)
Fair value, end of period	$	87

The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands):

	Year ended December 31,
	2013		2014
Fair value, beginning of period	$	—	$	158
Issuance of convertible preferred stock warrant		158		—
Change in fair value of Level 3 financial liabilities		—		(20	)
Fair value, end of period		158		138