Marketable Securities (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2014
Cash and cash equivalents:
Cash and money market funds	$	424,045	$	—	$	—		$	424,045
Total cash and cash equivalents	$	424,045	$	—	$	—		$	424,045
Marketable securities:
Government-sponsored enterprise securities (due within 1 year)	$	607,934	$	16	$	(28	)	$	607,922
Commercial paper (due within 1 year)	80,950		60		—			81,010
Corporate debt securities (due within 1 year)	196,420		18		(45		)	196,393
Corporate debt securities (due after 1 year through 5 years)	14,836		1		(7		)	14,830
Total marketable securities	$	900,140	$	95	$	(80	)	$	900,155
Total cash, cash equivalents and marketable securities	$	1,324,185	$	95	$	(80	)	$	1,324,200
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