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 March 31, 2019 and December 31, 2018, 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 March 31, 2019
(In thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	10,849	$	10,849	$	—	$	—		2.35	%
U.S. Government bonds and notes	41,479		41,482		—		(3		)	2.36	%
Corporate notes, bonds, commercial paper and other	212,149		212,209		3		(63		)	2.47	%
Total cash equivalents and marketable securities	264,477		264,540		3		(66		)
Cash	41,389		41,389		—		—
Total cash, cash equivalents and marketable securities	$	305,866	$	305,929	$	3	$	(66	)



	As of December 31, 2018
(In thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	10,080	$	10,080	$	—	$	—		2.23	%
U.S. Government bonds and notes	32,630		32,634		—		(4		)	2.28	%
Corporate notes, bonds, commercial paper and other	183,998		184,095		—		(97		)	2.37	%
Total cash equivalents and marketable securities	226,708		226,809		—		(101		)
Cash	51,056		51,056		—		—
Total cash, cash equivalents and marketable securities	$	277,764	$	277,865	$	—	$	(101	)

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



	As of
	March 31, 2019		December 31, 2018
	(In thousands)
Cash equivalents	$	101,627	$	64,868
Short term marketable securities	162,850		161,840
Total cash equivalents and marketable securities	264,477		226,708
Cash	41,389		51,056
Total cash, cash equivalents and marketable securities	$	305,866	$	277,764

The Company continues to invest in highly rated quality, highly liquid debt securities. As of March 31, 2019, 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 March 31, 2019 and December 31, 2018 are as follows:



	Fair Value				Gross Unrealized Loss
	March 31, 2019		December 31, 2018		March 31, 2019			December 31, 2018
	(In thousands)
Less than one year
U.S. Government bonds and notes	$	36,490	$	32,630	$	(3	)	$	(4	)
Corporate notes, bonds and commercial paper	183,849		183,998		(63		)	(97		)
Total Corporate notes, bonds, and commercial paper and U.S. Government bonds and notes	$	220,339	$	216,628	$	(66	)	$	(101	)

The gross unrealized loss at March 31, 2019 and December 31, 2018 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. There is no need to sell these investments, 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. 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.