Investments (Tables)

3 Months Ended

Mar. 31, 2014

Investments

Summary of investments

The following is a summary of our investments as of March 31, 2014 and December 31, 2013 (in thousands):

	March 31, 2014
			Gross		Gross			Estimated
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
Corporate debt securities
Due in one year or less	$	23,492	$	46	$	(2	)	$	23,536
Due in one to three years	108,536		159		(47		)	108,648
U.S. treasury and government agency securities
Due in one year or less	21,079		35		—			21,114
Due in one to three years	29,772		17		(28		)	29,761
Commercial paper
Due in one year or less	1,499		—		(1		)	1,498
Total investments	$	184,378	$	257	$	(78	)	$	184,557

	December 31, 2013
			Gross		Gross			Estimated
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
Corporate debt securities
Due in one year or less	$	42,609	$	44	$	(4	)	$	42,649
Due in one to three years	91,443		137		(106		)	91,474
U.S. treasury and government agency securities
Due in one year or less	18,526		19		—			18,545
Due in one to three years	34,123		37		(25		)	34,135
Total investments	$	186,701	$	237	$	(135	)	$	186,803