3. Investments

The following table summarizes unrealized gains and losses related to our investments designated as available-for-sale (dollars in thousands):


	As of December 31, 2012
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Certificates of deposit	$	2,804	$	—	$	—	$	2,804

Total investments	$	2,804	$	—	$	—	$	2,804


	As of December 31, 2011
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate obligations	$	11,260	$	—	$	(1	)	$	11,259
U.S. Government notes		14,049		7		(4	)		14,052
Auction rate municipal securities		893		9		—			902

Total investments	$	26,202	$	16	$	(5	)	$	26,213

The following table presents gross unrealized losses and fair values for those investments that were in an unrealized loss position aggregated by investment category and the length of time that individual securities have been in a continuous loss position (dollars in thousands):


	As of December 31, 2012				As of December 31, 2011
	Less than 12 Months				Less than 12 Months
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Corporate obligations	$	—	$	—	$	3,810	$	(1	)
U.S. Government notes		—		—		6,758		(4	)

	$	—	$	—	$	10,568	$	(5	)

There were no investments that were in an unrealized loss position for greater than 12 months at December 31, 2012 or 2011.

We realized gains of $3,000 and losses of $60,000 on sales of our marketable securities during the year ended December 31, 2012. We had realized gains of $52,000 and no losses and gains of $1.1 million and losses of $51,000 on the sale of marketable securities during the years ended December 31, 2011 and 2010, respectively.

We recognized $11,000 of other-than-temporary impairments to certain of our auction rate securities in 2012, $10,000 in 2011 and $86,000 in 2010. When evaluating investments for other-than-temporary impairment, we review factors such as the length of time and extent to which fair value has been below cost basis, the financial condition of the issuer of the investment securities and any changes thereto, and our intent to sell, or whether it is more-likely-than-not we would be required to sell the investment before recovery of the investment’s amortized cost basis.

The net carrying value and estimated fair value of debt and equity securities available for sale at December 31, 2012, by contractual maturity, are shown below (dollars in thousands). Expected maturities may differ from contractual maturities because the issuers of the securities may have the right or obligation to prepay obligations without prepayment penalties.


	Amortized Cost		Estimated Fair Value
Due in one year or less	$	2,804	$	2,804
Due after one year through three years		—		—
Due after three years		—		—

Total investment securities	$	2,804	$	2,804

Auction Rate Securities

During 2012 we redeemed our remaining auction rate securities with par value of $1.1 million at 75% of par value. At December 31, 2011, we held at par value $1.1 million of various auction rate securities. The assets underlying the auction rate instruments were primarily municipal bonds. In 2011, issuers called at par $25,000 of the related securities, and we redeemed an additional $1.1 million at 81% of original par value. We no longer hold any auction rate securities.