Investments (Tables)

6 Months Ended

Jun. 30, 2016

Investments

Summary of investments

The following is a summary of our investments as of June 30, 2016 and December 31, 2015 (in thousands):

	June 30, 2016
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Corporate debt securities
Due in one year or less	$	121,864	$	30	$	(40)	$	121,854
Due in one to three years		131,564		846		(36)		132,374
U.S. treasury and government agency securities
Due in one year or less		1,044		1		—		1,045
Due in one to three years		4,895		46		—		4,941
Commercial paper
Due in one year or less		32,644		—		—		32,644
Municipal securities
Due in one year or less		2,500		1		—		2,501
Total investments	$	294,511	$	924	$	(76)	$	295,359

	December 31, 2015
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Corporate debt securities
Due in one year or less	$	27,964	$	—	$	(38)	$	27,926
Due in one to three years		173,652		3		(904)		172,751
Commercial paper
Due in one year or less		34,452		2		(5)		34,449
Municipal securities
Due in one year or less		2,500		—		—		2,500
Total investments	$	238,568	$	5	$	(947)	$	237,626