Note 2—Cash Equivalents and Marketable Securities

At December 31, 2012 and 2011, cash equivalents primarily consisted of money market mutual funds and marketable securities primarily consisted of U.S. government and U.S. Government Sponsored Entities (GSE's), foreign government debt securities and high credit quality corporate debt securities. All marketable securities were considered available-for-sale and were carried at fair value on the Company's consolidated balance sheet. Short-term marketable securities mature twelve months or less from the date of the consolidated balance sheet and long-term marketable securities mature greater than twelve months from the date of the consolidated balance sheet.

Marketable securities are summarized as follows (in thousands):

Balance at December 31, 2012	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses Less than 12 Months			Gross Unrealized Losses 12 Months or Longer		Aggregate Fair Value

Corporate debt securities	$	110,540	$	13	$	(45	)	$	—	$	110,508
US government debt securities		59,811		7		(3	)		—		59,815
Foreign government debt securities		2,415		6		—			—		2,421

Total	$	172,766	$	26	$	(48	)	$	—	$	172,744

Balance at December 31, 2011	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses Less than 12 Months			Gross Unrealized Losses 12 Months or Longer		Aggregate Fair Value

Corporate debt securities	$	52,606	$	10	$	(11	)	$	—	$	52,605
US government debt securities		11,318		5		—			—		11,323
Foreign government debt securities		6,914		—		(17	)		—		6,897

Total	$	70,838	$	15	$	(28	)	$	—	$	70,825

The following table summarizes the contractual maturities of marketable securities at December 31, 2012 (in thousands):

	Amortized Cost		Aggregate Fair Value

Matures in less than one year	$	111,184	$	111,192
Matures in one to three years		61,582		61,552

Total	$	172,766	$	172,744

The following table summarizes marketable securities with unrealized losses by contractual maturity dates at December 31, 2012 (in thousands):

	Less than 12 Months					12 Months or Longer				Total

	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Corporate debt securities	$	70,191	$	(45	)	$	—	$	—	$	70,191	$	(45	)
US government debt securities		24,215		(3	)						24,215		(3	)

Total	$	94,406	$	(48	)	$	—	$	—	$	94,406	$	(48	)

Advent regularly reviews its investment portfolio to identify and evaluate investments that have indications of possible impairment. Factors considered in determining whether a loss is temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition, credit quality and near-term prospects of the investee, and Advent's ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value.

For fixed income securities that have unrealized losses as of December 31, 2012, the Company has determined that (i) it does not have the intent to sell any of these investments while in a loss position and (ii) it is not more likely than not that it will be required to sell any of these investments before recovery of the entire amortized cost basis. In addition, the Company has evaluated these fixed income securities and has determined that no credit losses exist. As of December 31, 2012, all securities in an unrealized loss position have been in an unrealized loss position for less than one year. The Company's management has determined that the unrealized losses on its fixed income securities as of December 31, 2012 were temporary in nature. Unrealized gains and losses are a component of "Accumulated other comprehensive income" in the accompanying consolidated balance sheets.

The Company had $16,000, $0 and $0 in realized gains related to marketable securities for the years ended December 31, 2012, 2011 and 2010, respectively.