Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2012

Marketable Securities

Schedule of available-for-sale securities, all of which have maturities of twelve months or less

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
	(in thousands)
December 31, 2012:
Certificate of deposit	$	240	$	—	$	—		$	240
Commercial paper		12,479				(14	)		12,465
Corporate debt securities		59,557		3		(27	)		59,533
Total	$	72,276	$	3	$	(41	)	$	72,238

Schedule of marketable securities in an unrealized loss position

	Aggregate Fair Value		Unrealized Losses
	(in thousands)
December 31, 2012:
Commercial paper		12,465		(14	)
Corporate debt securities		38,899		(27	)
	$	51,364		(41	)