Fair value measurements (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Assets 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, 2019
	Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash	$	1,909	$	1,909	$	—	$	—
Money market funds	72,696		72,696		—		—
Total cash and cash equivalents	74,605		74,605		—		—
Short-term investments:
U.S. Treasury bills	18,886		18,886		—		—
Corporate debt securities	91,244		—		91,244		—
Commercial paper	114,262		—		114,262		—
Other sovereign securities	1,988		—		1,988		—
Total short-term investments	226,380		18,886		207,494		—
Total	$	300,985	$	93,491	$	207,494	$	—

	December 31, 2018
	Total		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash	$	3,731	$	3,731	$	—	$	—
Money market funds	28,963		28,963		—		—
Total cash and cash equivalents	32,694		32,694		—		—
Short-term investments:
U.S. Treasury bills	3,771		3,771		—		—
Corporate debt securities	111,916		—		111,916		—
Commercial paper	74,409		—		74,409		—
Total short-term investments	190,096		3,771		186,325		—
Total	$	222,790	$	36,465	$	186,325	$	—