The following tables summarize, by major security type, the Company’s assets that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy and where they are classified on the Consolidated Balance Sheets:



	As of June 30, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	2,193,203	$	—	$	—		$	2,193,203
Level 1 securities:
Money market funds	105,603		—		—			105,603
Level 2 securities:
Corporate debt securities	271,569		419		(130		)	271,858
Government securities	197,919		364		(7		)	198,276
Certificate of deposits and commercial paper	6,100		—		—			6,100
Agency securities	26,621		31		—			26,652
Total	$	2,801,015	$	814	$	(137	)	$	2,801,692



	As of December 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	1,007,543	$	—	$	—		$	1,007,543
Level 1 securities:
Money market funds	111,759		—		—			111,759
Level 2 securities:
Corporate debt securities	295,500		432		(199		)	295,733
Government securities	168,749		120		(95		)	168,774
Asset and mortgage-backed securities	112		—		—			112
Certificate of deposits	3,600		—		—			3,600
Agency securities	26,665		5		(1		)	26,669
Total	$	1,613,928	$	557	$	(295	)	$	1,614,190



	As of
	June 30, 2015		December 31, 2014
	(in thousands)
Cash and cash equivalents	$	2,293,872	$	1,113,608
Short-term investments	502,886		494,888
Other non-current assets (1)	4,934		5,694
Total	$	2,801,692	$	1,614,190

(1) Primarily restricted cash that is related to workers compensation deposits.