Investments (Tables)

9 Months Ended

Sep. 30, 2013

Investments

Schedule of marketable investments classified as held-to-maturity

Marketable investments classified as held-to-maturity consist of the following (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Government-sponsored enterprises at September 30, 2013	$	421,890	$	342	$	(10	)	$	422,222
Corporate notes and bonds at September 30, 2013	294,284		125		(101		)	294,308
Total	$	716,174	$	467	$	(111	)	$	716,530
Reported under the following captions on the consolidated balance sheet at September 30, 2013:
Current marketable investments	$	394,612
Noncurrent marketable investments	321,562
	$	716,174

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Government-sponsored enterprises at December 31, 2012	$	350,043	$	261	$	(35	)	$	350,269
Corporate notes and bonds at December 31, 2012	280,385		184		(140		)	280,429
Total	$	630,428	$	445	$	(175	)	$	630,698
Reported under the following captions on the consolidated balance sheet at December 31, 2012:
Current marketable investments	$	325,175
Noncurrent marketable investments	305,253
	$	630,428

Summary of gross unrealized losses and the length of time marketable investments have been in a continuous unrealized loss position

The following table summarizes gross unrealized losses and the length of time marketable investments have been in a continuous unrealized loss position (in thousands):

	As of September 30, 2013					As of December 31, 2012
	Fair Value		Gross Unrealized Loss			Fair Value		Gross Unrealized Loss
Government-sponsored enterprises:
Continuous unrealized loss position less than one year	$	52,522	$	(10	)	$	72,727	$	(35	)
Continuous unrealized loss position greater than one year	—		—			—		—
	52,522		(10		)	72,727		(35		)
Corporate notes and bonds:
Continuous unrealized loss position less than one year	$	99,131	$	(101	)	$	90,960	$	(140	)
Continuous unrealized loss position greater than one year	—		—			—		—
	99,131		(101		)	90,960		(140		)
Total	$	151,653	$	(111	)	$	163,687	$	(175	)

Summary of the contractual maturities of held-to-maturity marketable investments

The following table summarizes the contractual maturities of held-to-maturity marketable investments (in thousands):

	September 30, 2013
	Amortized Cost		Fair Value
Due in less than one year	$	394,612	$	394,863
Due in one to two years	321,562		321,667
Due in three to five years	—		—
Due after five years	—		—
Total	$	716,174	$	716,530