Marketable Securities (Tables)

6 Months Ended

Jun. 30, 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 June 30, 2015
Cash and cash equivalents:
Cash and money market funds	$	870,543	$	—	$	—		$	870,543
Total cash and cash equivalents	$	870,543	$	—	$	—		$	870,543
Marketable securities:
Commercial paper (due within 1 year)	$	25,470	$	29	$	—		$	25,499
Corporate debt securities (due within 1 year)	120,430		12		(34		)	120,408
Total marketable securities	$	145,900	$	41	$	(34	)	$	145,907
Total cash, cash equivalents and marketable securities	$	1,016,443	$	41	$	(34	)	$	1,016,450
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