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 December 31, 2011, all of the Company's cash equivalents and marketable securities have 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 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	)

	As of December 31, 2010

(Dollars in thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	132,364	$	132,364	$	—	$	—			0.04	%
U.S. government sponsored obligations		266,817		266,840		29		(52	)		0.26	%
Corporate notes, bonds and commercial paper		95,724		95,773		8		(57	)		0.39	%

Total cash equivalents and marketable securities		494,905		494,977		37		(109	)
Cash		17,104		17,104		—		—

Total cash, cash equivalents and marketable securities	$	512,009	$	512,081	$	37	$	(109	)

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

	As of

	December 31, 2011		December 31, 2010
	(Dollars in thousands)
Cash equivalents	$	137,455	$	198,158
Short term marketable securities		127,212		296,747

Total cash equivalents and marketable securities		264,667		494,905
Cash		24,789		17,104

Total cash, cash equivalents and marketable securities	$	289,456	$	512,009

The Company continues to invest in high quality, highly liquid debt securities that mature within three years. As of December 31, 2011, these securities have a remaining maturity of less than one year. 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. As of December 31, 2011, certain marketable debt securities with a fair value of $137.1 million, which mature within one year, had insignificant unrealized losses. The unrealized loss, net, at December 31, 2011 was insignificant in relation to the Company's total available-for-sale portfolio. The unrealized loss, net, can be primarily attributed to a combination of market conditions as well as the demand for and duration of the Company's 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.

The estimated fair value of cash equivalents and marketable securities classified by date of contractual maturity and the length of time that the securities have been in a continuous unrealized loss position at December 31, 2011 and December 31, 2010 are as follows:

	As of				Unrealized Loss, net

	December 31, 2011		December 31, 2010		December 31, 2011			December 31, 2010
	(In thousands)
Less than one year	$	264,667	$	494,905	$	(100	)	$	(72	)

See Note 17, "Fair Value of Financial Instruments," for discussion regarding the fair value of the Company's cash equivalents and marketable securities.