Cash and Investments (Tables)

6 Months Ended

Jun. 30, 2016

Cash, cash equivalents and available-for-sale investments

The following table presents cash, cash equivalents, and available-for-sale marketable securities for the periods presented (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Market Value
June 30, 2016:
Cash	$	132,287	$	—	$	—		$	132,287
Cash equivalents:
Money market funds	419,858		—		—			419,858
US treasury securities	130,312		1		—			130,313
US agency securities	37,354		—		(5		)	37,349
Marketable securities:
Commercial paper	26,633		29		—			26,662
Certificates of deposit	10,000		5		—			10,005
US treasury securities	942,885		1,048		(11		)	943,922
US agency securities	446,114		400		(4		)	446,510
Corporate debt securities	1,151,409		5,309		(120		)	1,156,598
Municipal securities	8,000		12		—			8,012
Total cash, cash equivalents, and marketable securities	$	3,304,852	$	6,804	$	(140	)	$	3,311,516
December 31, 2015:
Cash	$	180,790	$	—	$	—		$	180,790
Cash equivalents:
Money market funds	276,898		—		—			276,898
Commercial paper	12,048		1		—			12,049
US treasury securities	24,999		1		—			25,000
US agency securities	51,500		—		—			51,500
Marketable securities:
Commercial paper	55,350		47		(23		)	55,374
US treasury securities	874,968		20		(959		)	874,029
US agency securities	606,924		17		(739		)	606,202
Corporate debt securities	1,029,463		96		(2,661		)	1,026,898
Municipal securities	10,636		6		—			10,642
Total cash, cash equivalents, and marketable securities	$	3,123,576	$	188	$	(4,382	)	$	3,119,382

Schedule of unrealized losses on investments in continuous unrealized loss position

The following table presents unrealized losses on investments by investment category and length of time the investment has been in a continuous unrealized loss position as of the periods presented (in thousands):



	Less than 12 months					12 Months or Greater					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
June 30, 2016:
Commercial paper	$	994	$	—		$	—	$	—		$	994	$	—
US treasury securities	93,320		(11		)	—		—			93,320		(11		)
US agency securities	60,195		(9		)	—		—			60,195		(9		)
Corporate debt securities	167,217		(110		)	9,677		(10		)	176,894		(120		)
Total	$	321,726	$	(130	)	$	9,677	$	(10	)	$	331,403	$	(140	)
December 31, 2015:
Commercial paper	$	28,482	$	(23	)	$	—	$	—		$	28,482	$	(23	)
US treasury securities	777,237		(959		)	—		—			777,237		(959		)
US agency securities	472,236		(739		)	—		—			472,236		(739		)
Corporate debt securities	943,276		(2,661		)	—		—			943,276		(2,661		)
Total	$	2,221,231	$	(4,382	)	$	—	$	—		$	2,221,231	$	(4,382	)

Available-for-sale investments by contractual maturity date

The following table presents available-for-sale marketable securities by contractual maturity date (in thousands) as of June 30, 2016:



	Amortized Cost		Estimated Fair Market Value
Due in one year or less	$	1,215,357	$	1,215,893
Due after one year through two years	1,009,638		1,012,282
Due after two years through three years	360,046		363,534
Total	$	2,585,041	$	2,591,709