Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2015

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, 2015
Cash and cash equivalents:
Cash and money market funds	$	664,879	$	—	$	—		$	664,879
Total cash and cash equivalents	$	664,879	$	—	$	—		$	664,879
Marketable securities:
Government-sponsored enterprise securities (due within 1 year)	$	284,126	$	5	$	(16	)	$	284,115
Commercial paper (due within 1 year)	59,688		57		—			59,745
Corporate debt securities (due within 1 year)	148,958		18		(24		)	148,952
Corporate debt securities (due after 1 year through 5 years)	23,430		13		—			23,443
Total marketable securities	$	516,202	$	93	$	(40	)	$	516,255
Total cash, cash equivalents and marketable securities	$	1,181,081	$	93	$	(40	)	$	1,181,134
As of December 31, 2014
Cash and cash equivalents:
Cash and money market funds	$	625,259	$	—	$	—		$	625,259
Total cash and cash equivalents	$	625,259	$	—	$	—		$	625,259
Marketable securities:
Government-sponsored enterprise securities (due within 1 year)	$	463,788	$	14	$	(52	)	$	463,750
Commercial paper (due within 1 year)	51,674		72		—			51,746
Corporate debt securities (due within 1 year)	196,065		2		(66		)	196,001
Corporate debt securities (due after 1 year through 5 years)	50,443		—		(93		)	50,350
Total marketable securities	$	761,970	$	88	$	(211	)	$	761,847
Total cash, cash equivalents and marketable securities	$	1,387,229	$	88	$	(211	)	$	1,387,106