Investments (Tables)

12 Months Ended

Dec. 31, 2014

Investments

Schedule of marketable investments classified as held-to-maturity

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

As of December 31, 2014	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Government-sponsored enterprises	$	127,212	$	118	$	(39	)	$	127,291
Corporate notes and bonds		293,288		260		(108	)		293,440
Total	$	420,500	$	378	$	(147	)	$	420,731
Reported under the following captions on the consolidated balance sheet:
Current marketable investments	$	297,842
Noncurrent marketable investments		122,658
	$	420,500

As of December 31, 2013	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Government-sponsored enterprises	$	445,939	$	257	$	(77	)	$	446,119
Corporate notes and bonds		411,455		300		(163	)		411,592
Total	$	857,394	$	557	$	(240	)	$	857,711
Reported under the following captions on the consolidated balance sheet:
Current marketable investments	$	409,645
Noncurrent marketable investments		447,749
	$	857,394

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 December 31,
	2014					2013
	Fair Value		Gross Unrealized Loss			Fair Value		Gross Unrealized Loss
Government-sponsored enterprises:
Continuous unrealized loss position less than one year	$	15,293	$	(39	)	$	76,651	$	(77	)
Continuous unrealized loss position greater than one year		—		—			—		—
		15,293		(39	)		76,651		(77	)
Corporate notes and bonds:
Continuous unrealized loss position less than one year		86,824		(97	)		168,669		(163	)
Continuous unrealized loss position greater than one year		3,443		(11	)		—		—
		90,267		(108	)		168,669		(163	)
Total	$	105,560	$	(147	)	$	245,320	$	(240	)

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):

	As of December 31, 2014
	Amortized Cost		Fair Value
Due in less than one year	$	297,842	$	297,969
Due in one to two years		107,405		107,522
Due in three to five years		15,253		15,240
Due after five years		—		—
Total	$	420,500	$	420,731