Fair value measurements (Tables)

3 Months Ended

Mar. 31, 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):

	March 31, 2016
	Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash	$	3,986	$	3,986	$	—	$	—
Money market funds	30,569		30,569		—		—
Total cash and cash equivalents	34,555		34,555		—		—
Short-term investments:
Corporate debt securities	26,024		—		26,024		—
Commercial paper	47,090		—		47,090		—
Total short-term investments	73,114		—		73,114		—
Total	$	107,669	$	34,555	$	73,114	$	—

	December 31, 2015
	Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash	$	757	$	757	$	—	$	—
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	49,375		19,632		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	$	122,209	$	19,632	$	102,577	$	—