Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2014

Cash and Cash Equivalents [Abstract]

Summary of cash, cash equivalents and marketable securities

A summary of the Company’s cash, cash equivalents and marketable securities is shown below:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(in thousands)
As of June 30, 2014
Cash and cash equivalents:
Cash and money market funds	$	420,558	$	—	$	—		$	420,558
Total cash and cash equivalents	$	420,558	$	—	$	—		$	420,558
Marketable securities:
Government-sponsored enterprise securities (due within 1 year)	$	497,601	$	8	$	(22	)	$	497,587
Commercial paper (due within 1 year)	69,144		99		—			69,243
Corporate debt securities (due within 1 year)	216,426		33		(26		)	216,433
Corporate debt securities (due after 1 year through 5 years)	15,335		5		—			15,340
Total marketable securities	$	798,506	$	145	$	(48	)	$	798,603
Total cash, cash equivalents and marketable securities	$	1,219,064	$	145	$	(48	)	$	1,219,161
As of December 31, 2013
Cash and cash equivalents:
Cash and money market funds	$	569,299	$	—	$	—		$	569,299
Total cash and cash equivalents	$	569,299	$	—	$	—		$	569,299
Marketable securities:
Government-sponsored enterprise securities (due within 1 year)	$	600,496	$	7	$	(53	)	$	600,450
Commercial paper (due within 1 year)	83,384		109		—			83,493
Corporate debt securities (due within 1 year)	189,674		14		(34		)	189,654
Corporate debt securities (due after 1 year through 5 years)	22,181		6		(7		)	22,180
Total marketable securities	$	895,735	$	136	$	(94	)	$	895,777
Total cash, cash equivalents and marketable securities	$	1,465,034	$	136	$	(94	)	$	1,465,076