4.	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
December 31, 2015
Cash and cash equivalents:
Cash	$	4,561	$	-	$	-		$	4,561
Money market funds		21,193		-		-			21,193
Corporate debt securities		19,052		7		(1	)		19,058
Total cash and cash equivalents		44,806		7		(1	)		44,812
Marketable securities available-for-sale:
U.S. government agency securities		17,628		-		(6	)		17,622
Corporate debt securities		133,679		71		(59	)		133,691
Total marketable securities available-for-sale		151,307		71		(65	)		151,313
Total cash, cash equivalents and marketable securities	$	196,113	$	78	$	(66	)	$	196,125
December 31, 2014
Cash and cash equivalents:
Cash	$	2,522	$	-	$	-		$	2,522
Money market funds		46,989		-		-			46,989
Total cash and cash equivalents		49,511		-		-			49,511
Marketable securities available-for-sale:
U.S. government agency securities		73,140		11		(10	)		73,141
Total marketable securities available-for-sale		73,140		11		(10	)		73,141
Total cash, cash equivalents and marketable securities	$	122,651	$	11	$	(10	)	$	122,652

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

	December 31, 2015
	Amortized Cost		Estimated Fair Value
Mature in one year or less	$	151,307	$	151,313
Mature after one year through two years		-		-
	$	151,307	$	151,313

There were no realized gains or losses from the sale of marketable securities in the years ended December 31, 2015, 2014 and 2013. All of our investments are classified as short-term and available-for-sale, as we may not hold our investments until maturity.