Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2013

Marketable Securities

Summary of marketable securities

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
March 31, 2013
Marketable securities
U.S. government and municipal obligations
Maturing in one year or less	$	21,016	$	30	$	—	$	21,046
Maturing after one year through three years	17,470		84		1		17,553
Total U.S. government and municipal obligations	$	38,486	$	114	$	1	$	38,599
Corporate debt securities
Maturing in one year or less	$	23,909	$	24	$	10	$	23,923
Maturing after one year through three years	44,253		6		31		44,228
Total corporate debt securities	$	68,162	$	30	$	41	$	68,151
Total marketable securities	$	106,648	$	144	$	42	$	106,750
December 31, 2012
Marketable securities
U.S. government and municipal obligations
Maturing in one year or less	$	15,566	$	28	$	—	$	15,594
Maturing after one year through three years	19,797		99		1		19,895
Total U.S. government and municipal obligations	$	35,363	$	127	$	1	$	35,489
Corporate debt securities
Maturing in one year or less	$	17,353	$	23	$	4	$	17,372
Maturing after one year through three years	6,193		14		3		6,204
Total corporate debt securities	$	23,546	$	37	$	7	$	23,576
Total marketable securities	$	58,909	$	164	$	8	$	59,065