3. Cash, cash equivalents and marketable securities

The following is a summary of cash, cash equivalents and available-for-sale marketable securities as of June 30, 2012 and December 31, 2011 (in thousands):


	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
June 30, 2012:
Cash and cash equivalents:
Cash	$	2,001	$	—	$	—		$	2,001
Money market funds		26,352		—		—			26,352
U.S. government agency securities		6,177		—		—			6,177

Total cash and cash equivalents		34,530		—		—			34,530
Marketable securities available-for-sale:
U.S. government agency securities		98,764		7		(34	)		98,737
Corporate debt securities		26,935		—		(3	)		26,932

Total marketable securities available-for-sale		125,699		7		(37	)		125,669

Total cash, cash equivalents and marketable securities	$	160,229	$	7	$	(37	)	$	160,199

December 31, 2011:
Cash and cash equivalents:
Cash	$	2,290	$	—	$	—		$	2,290
Money market funds		17,171		—		—			17,171
U.S. government agency securities		9,438		—		—			9,438
Corporate debt securities		3,044		—		(2	)		3,042

Total cash and cash equivalents		31,943		—		(2	)		31,941
Marketable securities available-for-sale:
U.S. Government agency securities		26,488		—		(6	)		26,482
Corporate debt securities		55,533		9		(4	)		55,538

Total marketable securities available-for-sale		82,021		9		(10	)		82,020

Total cash, cash equivalents and marketable securities	$	113,964	$	9	$	(12	)	$	113,961

The following is a summary of the amortized cost and estimated fair value of available-for-sale securities at June 30, 2012, by contractual maturity (in thousands):


	June 30, 2012
	Amortized Cost		Estimated Fair Value
Mature in one year or less	$	68,935	$	68,927
Mature after one year through two years		56,764		56,742

	$	125,699	$	125,669

There were no realized gains or losses from the sale of marketable securities in the three and six months ended June 30, 2012 and 2011. All of our investments are classified as short-term and available-for-sale, as we may not hold our investments until maturity. The corporate debt securities held as of June 30, 2012 and December 31, 2011 were secured by the Federal Deposit Insurance Corporation through the Temporary Liquidity Guarantee Program.