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 December 31, 2017 and 2016, 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, 2017
(Dollars in thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	10,915	$	10,915	$	—	$	—		1.16	%
U.S. Government bonds and notes	55,220		55,221		—		(1		)	1.12	%
Corporate notes, bonds, commercial paper and other	195,073		195,204		—		(131		)	1.39	%
Total cash equivalents and marketable securities	261,208		261,340		—		(132		)
Cash	68,168		68,168		—		—
Total cash, cash equivalents and marketable securities	$	329,376	$	329,508	$	—	$	(132	)



	As of December 31, 2016
(Dollars in thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	10,681	$	10,681	$	—	$	—		0.41	%
U.S. Government bonds and notes	48,292		48,291		1		—			0.39	%
Corporate notes, bonds, commercial paper and other	62,178		62,199		—		(21		)	0.66	%
Total cash equivalents and marketable securities	121,151		121,171		1		(21		)
Cash	51,031		51,031		—		—
Total cash, cash equivalents and marketable securities	$	172,182	$	172,202	$	1	$	(21	)

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



	As of
	December 31, 2017		December 31, 2016
	(Dollars in thousands)
Cash equivalents	$	157,676	$	84,263
Short term marketable securities	103,532		36,888
Total cash equivalents and marketable securities	261,208		121,151
Cash	68,168		51,031
Total cash, cash equivalents and marketable securities	$	329,376	$	172,182

The Company continues to invest in highly rated quality, highly liquid debt securities. As of December 31, 2017, 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.

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 December 31, 2017 and 2016 are as follows:



	Fair Value				Gross Unrealized Loss
	December 31, 2017		December 31, 2016		December 31, 2017			December 31, 2016
	(In thousands)
Less than one year
U.S. Government bonds and notes	$	42,581	$	18,395	$	(1	)	$	—
Corporate notes, bonds and commercial paper	194,015		54,377		(131		)	(21		)
Total Corporate notes, bonds, and commercial paper and U.S. Government bonds and notes	$	236,596	$	72,772	$	(132	)	$	(21	)

The gross unrealized loss at December 31, 2017 and 2016 was not material in relation to the Company’s total available-for-sale portfolio. The gross unrealized loss can be primarily attributed to a combination of market conditions as well as the demand for and duration of the U.S. government-sponsored obligations and 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 8, “Fair Value of Financial Instruments,” for discussion regarding the fair value of the Company’s cash equivalents and marketable securities.