Fair value measurements (Tables)

6 Months Ended

Jun. 30, 2016

Fair Value Disclosures [Abstract]

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

The following tables summarize the assets and liabilities measured at fair value on a recurring basis (in thousands):

	June 30, 2016
	Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash	$	3,570	$	3,570	$	—	$	—
Money market funds	19,472		19,472		—		—
Corporate debt securities	1,500		—		1,500		—
Total cash and cash equivalents	24,542		23,042		1,500		—
Short-term investments:
Corporate debt securities	27,184		—		27,184		—
Commercial paper	39,587		—		39,587		—
Total short-term investments	66,771		—		66,771		—
Total	$	91,313	$	23,042	$	68,271	$	—

	December 31, 2015
	Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash	$	875	$	875	$	—	$	—
Money market funds	18,875		18,875		—		—
Corporate debt securities	6,749		—		6,749		—
Commercial paper	22,994		—		22,994		—
Total cash and cash equivalents	49,493		19,750		29,743		—
Short-term investments:
Corporate debt securities	27,622		—		27,622		—
Commercial paper	45,212		—		45,212		—
Total short-term investments	72,834		—		72,834		—
Total	$	122,327	$	19,750	$	102,577	$	—