Investments (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Summary of amortized cost, and gross unrealized gains and losses on all securities

	Amortized cost		Gross unrealized gains		Gross unrealized losses		Fair value
	(in thousands)
Short-term investments:
Commercial paper	$	4,994	$	—	$	1	$	4,993
Corporate notes/bonds		1,458		—		—		1,458
Total short-term investments	$	6,452	$	—	$	1	$	6,451

Summary of financial assets measured at fair value on a recurring basis

	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents:
Money market funds	$	4,575	$	—	$	—	$	4,575
Investments:
Available-for-sales securities—current:
Commercial paper		—		4,993		—		4,993
Corporate notes/bonds		—		1,458		—		1,458
Total	$	4,575	$	6,451	$	—	$	11,026

	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents:
Money market funds	$	10,949	$	—	$	—	$	10,949
Investments:
Available-for-sales securities—current:
FDIC guaranteed certificates of deposit		—		—		—		—
Corporate notes/bonds		—		—		—		—
Total	$	10,949	$	—	$	—	$	10,949