The following is a summary of our investments as of March 31, 2017 and December 31, 2016 (in thousands):



	March 31, 2017
			Gross		Gross			Estimated
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
Corporate debt securities
Due in one year or less	$	137,390	$	8	$	(86	)	$	137,312
Due in one to three years	111,161		36		(135		)	111,062
U.S. treasury and government agency securities
Due in one year or less	2,513		—		(1		)	2,512
Due in one to three years	14,373		4		(49		)	14,328
Commercial paper
Due in one year or less	26,875		—		—			26,875
Certificates of deposit
Due in one year or less	12,000		—		—			12,000
Due in one to three years	1,452		—		—			1,452
Total investments	$	305,764	$	48	$	(271	)	$	305,541



	December 31, 2016
			Gross		Gross			Estimated
	Amortized		Unrealized		Unrealized			Fair
	Cost		Gains		Losses			Value
Corporate debt securities
Due in one year or less	$	106,430	$	3	$	(69	)	$	106,364
Due in one to three years	139,742		32		(281		)	139,493
U.S. treasury and government agency securities
Due in one year or less	1,021		—		—			1,021
Due in one to three years	11,395		—		(52		)	11,343
Commercial paper
Due in one year or less	40,560		—		—			40,560
Certificates of deposit
Due in one year or less	6,000		—		—			6,000
Total investments	$	305,148	$	35	$	(402	)	$	304,781