Short-term Investments (Tables)

9 Months Ended

Sep. 30, 2015

Short-Term Investments And Fair Value Measurement [Abstract]

Available-For-Sale Securities Reported at Fair Value

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 September 30, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	2,008,627	$	—	$	—		$	2,008,627
Level 1 securities:
Money market funds	115,316		—		—			115,316
Level 2 securities:
Corporate debt securities	251,192		406		(467		)	251,131
Government securities	212,256		599		(9		)	212,846
Certificate of deposits	3,600		—		—			3,600
Agency securities	26,599		29		—			26,628
Total	$	2,617,590	$	1,034	$	(476	)	$	2,618,148

	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
	September 30, 2015		December 31, 2014
	(in thousands)
Cash and cash equivalents	$	2,115,437	$	1,113,608
Short-term investments	494,205		494,888
Other non-current assets (1)	8,506		5,694
Total	$	2,618,148	$	1,614,190

(1) Primarily restricted cash that is related to workers compensation deposits and letter of credit agreements.

Estimated Fair Value of Short-Term Investments by Contractual Maturity

The estimated fair value of short-term investments by contractual maturity as of September 30, 2015 is as follows:

	(in thousands)
Due within one year	$	155,330
Due after one year and through five years	338,875
Total short-term investments	$	494,205