3. Cash, Cash Equivalents, Restricted Cash and Marketable Securities

The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheet that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows:

	September 30, 2018		December 31, 2017
Cash and cash equivalents	$	38,712	$	26,584
Restricted cash		622		629
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statements of cash flows	$	39,334	$	27,213

Due to the adoption of ASU 2016-18, we have presented below, comparable prior period cash, cash equivalents and restricted cash balances as presented in the condensed consolidated statement of cash flows:

	September 30, 2017		December 31, 2016
Cash and cash equivalents	$	20,096	$	24,289
Restricted cash		626		602
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statements of cash flows	$	20,722	$	24,891

Restricted cash balances relate to certificates of deposit issued as collateral to certain letters of credit issued as security to our lease arrangements. See Note 6.

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

	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
September 30, 2018
Cash and cash equivalents:
Cash	$	4,515	$	-	$	-		$	4,515
Money market funds		22,697		-		-			22,697
U.S. treasuries		11,500		-		-			11,500
Total cash and cash equivalents		38,712		-		-			38,712
Marketable securities available-for-sale:
U.S. treasuries		25,694		-		(18	)		25,676
U.S. government agency securities		45,329		-		(70	)		45,259
Corporate debt securities		70,580		2		(8	)		70,574
Total marketable securities available-for-sale		141,603		2		(96	)		141,509
Total cash, cash equivalents and marketable securities	$	180,315	$	2	$	(96	)	$	180,221
December 31, 2017
Cash and cash equivalents:
Cash	$	4,041	$	-	$	-		$	4,041
Money market funds		22,543		-		-			22,543
Total cash and cash equivalents		26,584		-		-			26,584
Marketable securities available-for-sale:
U.S. treasuries		45,559		-		(25	)		45,534
U.S. government agency securities		86,860		-		(40	)		86,820
Corporate debt securities		32,931		-		(15	)		32,916
Total marketable securities available-for-sale		165,350		-		(80	)		165,270
Total cash, cash equivalents and marketable securities	$	191,934	$	-	$	(80	)	$	191,854

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

	September 30, 2018
	Amortized Cost		Estimated Fair Value
Mature in one year or less	$	141,603	$	141,509
Mature after one year through two years		-		-
	$	141,603	$	141,509

There were no realized gains or losses from the sale of marketable securities during the nine months ended September 30, 2018 and 2017.

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;

•

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.