3. Cash, cash equivalents and marketable securities

The following is a summary of cash, cash equivalents and marketable securities available-for-sale as of March 31, 2013 and December 31, 2012 (in thousands):


	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
March 31, 2013
Cash and cash equivalents:
Cash	$	2,567	$	—	$	—		$	2,567
Money market funds		18,783		—		—			18,783
U.S. government agency securities		2,201		—		—			2,201
U.S. treasury securities		750							750
Municipal securities		715		—		—			715

Total cash and cash equivalents		25,016		—		—			25,016

Marketable securities available-for-sale:
U.S. government agency securities		77,821		36		—			77,857
U.S. treasury securities		2,499		1		—			2,500

Total marketable securities available-for-sale		80,320		37		—			80,357

Total cash, cash equivalents and marketable securities	$	105,336	$	37	$	—		$	105,373

December 31, 2012
Cash and cash equivalents:
Cash	$	1,542	$	—	$	—		$	1,542
Money market funds		3,140		—		—			3,140
U.S. government agency securities		2,202		—		—			2,202
Municipal securities		715		—		—			715

Total cash and cash equivalents		7,599		—		—			7,599

Marketable securities available-for-sale:
U.S. government agency securities		116,986		46		(1	)		117,031
U.S. treasury securities		500		—		—			500

Total marketable securities available-for-sale		117,486		46		(1	)		117,531

Total cash, cash equivalents and marketable securities	$	125,085	$	46	$	(1	)	$	125,130

The following is a summary of the amortized cost and estimated fair value of marketable securities available-for-sale at March 31, 2013, by contractual maturity (in thousands):


	March 31, 2013
	Amortized Cost		Estimated Fair Value
Mature in one year or less	$	61,367	$	61,393
Mature after one year through two years		18,953		18,964

	$	80,320	$	80,357

We have classified our entire investment portfolio as available-for-sale. We view our available-for-sale portfolio as 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 income (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;

•

the duration to maturity of our investments;

•

our intention to hold the investments 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 basis;

•

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.