Fair Value Measurements - (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Summary of valuation of the Company's investments and financial instruments that are measured at fair value on a recurring basis

The following table summarizes the valuation of the Company’s financial instruments that are measured at fair value on a recurring basis:

	June 30, 2019								December 31, 2018
			Fair value measurement category								Fair value measurement category
(In thousands)	Total		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	4,831	$	4,831	$	—	$	—	$	5,838	$	5,838	$	—	$	—
Repurchase agreements	—		—		—		—		5,000		—		5,000		—
Commercial paper	17,149		—		17,149		—		30,710		—		30,710		—
Corporate notes	17,245		—		17,245		—		13,144		—		13,144		—
U.S. government securities	6,966		—		6,966		—		10,166		—		10,166		—
U.S. asset-backed securities	10,687		—		10,687		—		10,618		—		10,618		—
	$	56,878	$	4,831	$	52,047	$	—	$	75,476	$	5,838	$	69,638	$	—