6. Marketable Securities

Rambus invests its excess cash and cash equivalents primarily in U.S. government sponsored obligations, commercial paper, corporate notes and bonds, money market funds and municipal notes and bonds that mature within three years. As of September 30, 2012 and December 31, 2011, all of the Company’s cash equivalents and marketable securities had a remaining maturity of less than one year.

All cash equivalents and marketable securities are classified as available-for-sale. Total cash, cash equivalents and marketable securities are summarized as follows:



	As of September 30, 2012
(Dollars in thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	118,508	$	118,508	$	—	$	—		0.01	%
Corporate notes, bonds and commercial paper	56,886		56,906		—		(20		)	0.21	%
Total cash equivalents and marketable securities	175,394		175,414		—		(20		)
Cash	31,692		31,692		—		—
Total cash, cash equivalents and marketable securities	$	207,086	$	207,106	$	—	$	(20	)



	As of December 31, 2011
(Dollars in thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	127,559	$	127,559	$	—	$	—		0.01	%
Corporate notes, bonds and commercial paper	137,108		137,208		—		(100		)	0.29	%
Total cash equivalents and marketable securities	264,667		264,767		—		(100		)
Cash	24,789		24,789		—		—
Total cash, cash equivalents and marketable securities	$	289,456	$	289,556	$	—	$	(100	)

Available-for-sale securities are reported at fair value on the balance sheets and classified as follows:



	September 30, 2012		December 31, 2011
	(Dollars in thousands)
Cash equivalents	$	120,514	$	137,455
Short term marketable securities	54,880		127,212
Total cash equivalents and marketable securities	175,394		264,667
Cash	31,692		24,789
Total cash, cash equivalents and marketable securities	$	207,086	$	289,456

The Company continues to invest in highly rated, highly liquid debt securities. The Company holds all of its marketable securities as available-for-sale, marks them to market and regularly reviews its portfolio to ensure adherence to its investment policy and to monitor individual investments for risk analysis, proper valuation and unrealized losses that may be other than temporary.

The estimated fair value of cash equivalents and marketable securities classified by the length of time that the securities have been in a continuous unrealized loss position at September 30, 2012 and December 31, 2011 are as follows:



	Fair Value				Gross Unrealized Loss
	September 30, 2012		December 31, 2011		September 30, 2012			December 31, 2011
	(In thousands)
Less than one year
Corporate notes, bonds and commercial paper	$	46,384	$	137,107	$	(20	)	$	(100	)

The unrealized loss at September 30, 2012 was insignificant in relation to the Company’s total available-for-sale portfolio. The unrealized loss can be primarily attributed to a combination of market conditions as well as the demand for and duration of the corporate notes and bonds. The Company has no intent to sell, there is no requirement to sell and the Company believes that it can recover the amortized cost of these investments. The Company has found no evidence of impairment due to credit losses in its portfolio. Therefore, these unrealized losses were recorded in other comprehensive income (loss). However, the Company cannot provide any assurance that its portfolio of cash, cash equivalents and marketable securities will not be impacted by adverse conditions in the financial markets, which may require the Company in the future to record an impairment charge for credit losses which could adversely impact its financial results.

See Note 14, “Fair Value of Financial Instruments,” for discussion regarding the fair value of the Company’s cash equivalents and marketable securities.