5. Investments

Marketable Investments

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

As of June 30, 2015	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Government-sponsored enterprises	$	87,632	$	61	$	(30	)	$	87,663
Corporate notes and bonds	219,609		251		(10		)	219,850

Total	$	307,241	$	312	$	(40	)	$	307,513

Reported under the following captions on the consolidated balance sheet:
Current marketable investments	$	185,774
Noncurrent marketable investments	121,467

	$	307,241

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

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 June 30, 2015					As of December 31, 2014
	Fair Value		Gross Unrealized Loss			Fair Value		Gross Unrealized Loss
Government-sponsored enterprises:
Continuous unrealized loss position less than one year	$	25,288	$	(30	)	$	15,293	$	(39	)
Continuous unrealized loss position greater than one year	—		—			—		—

	25,288		(30		)	15,293		(39		)
Corporate notes and bonds:
Continuous unrealized loss position less than one year	14,493		(10		)	86,824		(97		)
Continuous unrealized loss position greater than one year	—		—			3,443		(11		)

	14,493		(10		)	90,267		(108		)

Total	$	39,781	$	(40	)	$	105,560	$	(147	)

We attribute gross unrealized losses pertaining to our held-to-maturity securities as of June 30, 2015 and December 31, 2014 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 do not believe that these securities 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):

	June 30, 2015
	Amortized Cost		Fair Value
Due in less than one year	$	185,774	$	185,916
Due in one to two years	121,467		121,597
Due in three to five years	—		—
Due after five years	—		—

Total	$	307,241	$	307,513

Investments Held at Cost

As of June 30, 2015, we maintain in the aggregate, non-controlling equity investments of $87.2 million in privately-held corporations, including a $50.0 million investment in the preferred stock of Synthetic Genomics Inc. (SGI), which we purchased in May 2014. We account for these investments under the cost method since we do not have the ability to exercise significant influence over these companies and their fair values are not readily determinable. The fair value of these investments has not been estimated at June 30, 2015, as we have not identified any events or developments indicating that their carrying amounts may be impaired. We include these investments within other assets on our accompanying consolidated balance sheets.