3. Cash, cash equivalents and marketable securities

Cash, cash equivalents and marketable securities consist of the following (in thousands):

	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
September 30, 2017
Cash and cash equivalents:
Cash	$	2,972	$	-	$	-		$	2,972
Money market funds		14,124		-		-			14,124
Corporate debt securities		3,000		-		-			3,000
Total cash and cash equivalents		20,096		-		-			20,096
Marketable securities available-for-sale:
U.S. Treasuries		33,664		-		(15	)		33,649
U.S. government agency securities		95,748		-		(17	)		95,731
Corporate debt securities		42,200		4		-			42,204
Total marketable securities available-for-sale		171,612		4		(32	)		171,584
Total cash, cash equivalents and marketable securities	$	191,708	$	4	$	(32	)	$	191,680
December 31, 2016
Cash and cash equivalents:
Cash	$	3,557	$	-	$	-		$	3,557
Money market funds		18,981		-		-			18,981
U.S. government agency securities		1,751		-		-			1,751
Total cash and cash equivalents		24,289		-		-			24,289
Marketable securities available-for-sale:
U.S. Treasuries		3,499		-		-			3,499
U.S. government agency securities		28,685		3		(2	)		28,686
Corporate debt securities		24,938		5		(2	)		24,941
Total marketable securities available-for-sale		57,122		8		(4	)		57,126
Total cash, cash equivalents and marketable securities	$	81,411	$	8	$	(4	)	$	81,415

The maturities of our marketable securities available-for-sale are as follows (in thousands):

	September 30, 2017
	Amortized Cost		Estimated Fair Value
Mature in one year or less	$	171,612	$	171,584
Mature after one year through two years		-		-
	$	171,612	$	171,584

There were no realized gains or losses from the sale of marketable securities during the nine months ended September 30, 2017 and 2016.

We have classified our entire investment portfolio as available-for-sale and available for use in current operations and accordingly have classified all investments as short-term. Available-for-sale securities are carried at fair value based on inputs that are observable, either directly or indirectly, such as quoted market prices for similar securities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the securities, with unrealized gains and losses included in accumulated other comprehensive loss in stockholders’ equity. Realized gains and losses and declines in value, if any, judged to be other than temporary on available-for-sale securities are included in interest income or expense. The cost of securities sold is based on the specific identification method. Management assesses whether declines in the fair value of investment securities are other than temporary. In determining whether a decline is other than temporary, management considers the following factors:

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Whether the investment has been in a continuous realized loss position for over 12 months;

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the duration to maturity of our investments;

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our intention and ability to hold the investment to maturity and if it is not more likely than not that we will be required to sell the investment before recovery of the amortized cost bases;

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the credit rating, financial condition and near-term prospects of the issuer; and

•

the type of investments made.

To date, there have been no declines in fair value that have been identified as other than temporary.