5. Investments

Marketable Investments

Held-to-Maturity Investments

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

As of March 31, 2014	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Government-sponsored enterprises	$	316,197	$	284	$	(69	)	$	316,412
Corporate notes and bonds	414,268		522		(125		)	414,665
Total	$	730,465	$	806	$	(194	)	$	731,077
Reported under the following captions on the consolidated balance sheet:
Current marketable investments	$	346,698
Noncurrent marketable investments	383,767
	$	730,465

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

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 March 31, 2014					As of December 31, 2013
	Fair Value		Gross Unrealized Loss			Fair Value		Gross Unrealized Loss
Government-sponsored enterprises:
Continuous unrealized loss position less than one year	$	58,329	$	(69	)	$	76,651	$	(77	)
Continuous unrealized loss position greater than one year	—		—			—		—
	58,329		(69		)	76,651		(77		)
Corporate notes and bonds:
Continuous unrealized loss position less than one year	121,352		(125		)	168,669		(163		)
Continuous unrealized loss position greater than one year	—		—			—		—
	121,352		(125		)	168,669		(163		)
Total	$	179,681	$	(194	)	$	245,320	$	(240	)

We attribute gross unrealized losses pertaining to our held-to-maturity securities as of March 31, 2014 and December 31, 2013 to the variability in related market interest rates. We do not intend to sell these securities, nor is it more likely than not that we will be required to sell them prior to the end of their contractual terms. Furthermore, we believe these securities do not expose us to undue market risk or counterparty credit risk. As such, we do not consider these securities to be other than temporarily impaired.

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

	March 31, 2014
	Amortized Cost		Fair Value
Due in less than one year	$	346,698	$	346,868
Due in one to two years	246,705		247,037
Due in three to five years	137,062		137,172
Due after five years	—		—
Total	$	730,465	$	731,077