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Marketable Securities

6 Months Ended

Jun. 30, 2011

6. Marketable Securities

Rambus invests its excess cash and cash equivalents primarily in U.S. government agency and treasury notes, commercial paper, corporate notes and bonds, money market funds and municipal notes and bonds that mature within three years.

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

	June 30, 2011
(Dollars in thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	168,847	$	168,847	$	—	$	—		0.01	%
U.S. government bonds and notes	65,592		65,569		23		—			0.22	%
Corporate notes, bonds and commercial paper	113,958		114,020		2		(64		)	0.40	%
Total cash equivalents and marketable securities	348,397		348,436		25		(64		)
Cash	10,957		10,957		—		—
Total cash, cash equivalents and marketable securities	$	359,354	$	359,393	$	25	$	(64	)

	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 bonds and notes	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:

	June 30, 2011		December 31, 2010
	(in thousands)
Cash equivalents	$	168,847	$	198,158
Short term marketable securities	179,550		296,747
Total cash equivalents and marketable securities	348,397		494,905
Cash	10,957		17,104
Total cash, cash equivalents and marketable securities	$	359,354	$	512,009

The Company continues to invest in high quality, highly liquid debt securities that mature within three years. 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 June 30, 2011, certain marketable debt securities with a fair value of $91.4 million, which mature within one year, had insignificant unrealized losses. The unrealized loss, net, at June 30, 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 U.S. government bonds and notes. 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 associated unrealized loss, net, at June 30, 2011 and December 31, 2010 are as follows:

	As of				Unrealized Loss, net
	June 30, 2011		December 31, 2010		June 30, 2011			December 31, 2010
	(in thousands)
Contractual maturity:
Due within one year	$	348,397	$	494,905	$	(39	)	$	(72	)

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