Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2016

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)
December 31, 2016
Cash and cash equivalents:
Cash and money market funds	$	1,183,945	$	—	$	—		$	1,183,945
Total cash and cash equivalents	$	1,183,945	$	—	$	—		$	1,183,945
Marketable securities:
Government-sponsored enterprise securities (matures within 1 year)	$	15,506	$	2	$	—		$	15,508
Corporate equity securities (matures within 1 year)	43,213		21,347		—			64,560
Commercial paper (matures within 1 year)	59,331		73		—			59,404
Corporate debt securities (matures within 1 year)	111,225		—		(85		)	111,140
Total marketable securities	229,275		21,422		(85		)	250,612
Total cash, cash equivalents and marketable securities	$	1,413,220	$	21,422	$	(85	)	$	1,434,557
December 31, 2015
Cash and cash equivalents:
Cash and money market funds	$	582,352	$	—	$	—		$	582,352
Government-sponsored enterprise securities	85,994		—		—			85,994
Commercial paper	34,889		—		—			34,889
Corporate debt securities	11,533		—		—			11,533
Total cash and cash equivalents	$	714,768	$	—	$	—		$	714,768
Marketable securities:
Government-sponsored enterprise securities (matures within 1 year)	$	87,176	$	—	$	(14	)	$	87,162
Commercial paper (matures within 1 year)	98,877		246		—			99,123
Corporate debt securities (matures within 1 year)	141,515		—		(106		)	141,409
Total marketable securities	327,568		246		(120		)	327,694
Total cash, cash equivalents and marketable securities	1,042,336		246		(120		)	1,042,462