Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2018

Marketable Securities

Summary of marketable securities, classified as available-for-sale

			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
	(In thousands)
December 31, 2018
Marketable securities
U.S. government and municipal obligations
Maturing in one year or less	$	27,355	$	—	$	(4)	$	27,351
Maturing after one year through three years		—		—		—		—
Total U.S. government and municipal obligations	$	27,355	$	—	$	(4)	$	27,351
Corporate debt securities
Maturing in one year or less	$	42,370	$	—	$	(9)	$	42,361
Maturing after one year through three years		—		—		—		—
Total corporate debt securities	$	42,370	$	—	$	(9)	$	42,361
Total marketable securities	$	69,725	$	—	$	(13)	$	69,712
December 31, 2017
Marketable securities
U.S. government and municipal obligations
Maturing in one year or less	$	26,164	$	3	$	(9)	$	26,158
Maturing after one year through three years		—		—		—		—
Total U.S. government and municipal obligations	$	26,164	$	3	$	(9)	$	26,158
Corporate debt securities
Maturing in one year or less	$	73,007	$	1	$	(27)	$	72,981
Maturing after one year through three years		—		—		—		—
Total corporate debt securities	$	73,007	$	1	$	(27)	$	72,981
Total marketable securities	$	99,171	$	4	$	(36)	$	99,139