Fair value measurements (Tables)

3 Months Ended

Mar. 31, 2018

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 measured at fair value on a recurring basis (in thousands):

	March 31, 2018
	Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash	$	3,721	$	3,721	$	—	$	—
Money market funds	16,846		16,846		—		—
Total cash and cash equivalents	20,567		20,567		—		—
Short-term investments:
Corporate debt securities	86,219		—		86,219		—
Commercial paper	41,866		—		41,866		—
Total short-term investments	128,085		—		128,085		—
Total	$	148,652	$	20,567	$	128,085	$	—

	December 31, 2017
	Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash	$	1,026	$	1,026	$	—	$	—
Money market funds	106,677		106,677		—		—
Total cash and cash equivalents	107,703		107,703		—		—
Short-term investments:
Corporate debt securities	24,241		—		24,241		—
Commercial paper	18,893		—		18,893		—
Total short-term investments	43,134		—		43,134		—
Total	$	150,837	$	107,703	$	43,134	$	—