Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2017

Marketable Securities

Schedule of marketable securities

			Gross		Gross
	Amortized		Unrealized		Unrealized
March 31, 2017	Cost		Gains		Losses		Fair Value
(in thousands)
Money Market Funds	$	11,057	$	—	$	—	$	11,057
Corporate Securities		165,269		10		(597)		164,682
Government Securities		215,008		16		(616)		214,408
	$	391,334	$	26	$	(1,213)	$	390,147
Reported as
Cash and cash equivalents							$	11,057
Marketable securities								379,090
Total investments							$	390,147
			Gross		Gross
	Amortized		Unrealized		Unrealized
December 31, 2016	Cost		Gains		Losses		Fair Value
(in thousands)
Money Market Funds	$	12,137	$	—	$	—	$	12,137
Corporate Securities		182,394		6		(917)		181,483
Government Securities		207,986		44		(565)		207,465
	$	402,517	$	50	$	(1,482)	$	401,085
Reported as
Cash and cash equivalents							$	12,137
Marketable securities								388,948
Total investments							$	401,085

Schedule of maturities of marketable securities

	Amortized		Estimated
March 31, 2017	Cost		Fair Value
(in thousands)
Mature in one year or less	$	141,371	$	141,225
Mature after one year		238,906		237,865
	$	380,277	$	379,090
	Amortized		Estimated
December 31, 2016	Cost		Fair Value
(in thousands)
Mature in one year or less	$	115,748	$	115,608
Mature after one year		274,632		273,340
	$	390,380	$	388,948

Schedule of unrealized losses on available-for-sale investments

The unrealized losses on available-for-sale investments and their related fair values as of March 31, 2017 and December 31, 2016 are as follows:

	Less than 12 months				12 months or greater
March 31, 2017		Fair value		Unrealized losses		Fair value		Unrealized losses
(in thousands)
Corporate Securities	$	78,164	$	(82)	$	72,512	$	(515)
Government Securities		48,472		(71)		141,980		(545)
	$	126,636	$	(153)	$	214,492	$	(1,060)
	Less than 12 months				12 months or greater
December 31, 2016		Fair value		Unrealized losses		Fair value		Unrealized losses
(in thousands)
Corporate Securities	$	82,215	$	(133)	$	88,990	$	(784)
Government Securities		17,573		(16)		149,694		(549)
	$	99,787	$	(149)	$	238,684	$	(1,333)