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, 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


	As of December 31, 2010
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate obligations	$	16,445	$	1	$	—		$	16,446
U.S. Government notes		13,632		—		(30	)		13,602
Municipal securities		1,006		2		—			1,008
Auction rate municipal securities		924		27		—			951
Auction rate preferred securities		891		—		—			891

Total investments	$	32,898	$	30	$	(30	)	$	32,898

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, 2011					As of December 31, 2010
	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	)		12,225		(30	)

	$	10,568	$	(5	)	$	12,225	$	(30	)

There were no investments that were in an unrealized loss position for greater than 12 months at December 31, 2011 or 2010.

We realized gains of $52,000 and no losses on sales of our marketable securities during the year ended December 31, 2011. We had realized gains of $1.1 million and losses of $51,000 and gains of $413,000 and no realized losses on the sale of marketable securities during the years ended December 31, 2010 and 2009, respectively.

We recognized $10,000 of other-than-temporary impairments to certain of our auction rate securities in 2011 and $86,000 in 2010. The auction rate securities impaired in 2010 were redeemed in January 2011 at 81% of their par value. Given the duration and extent of the decline in fair values associated with our equity securities (comprised primarily of various equity mutual funds), and auction rate securities, we recognized an other-than-temporary impairment of $365,000, before tax, during the year ended December 31, 2009. We sold these equity securities in April 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, 2011, 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	$	25,309	$	25,311
Due after one year through three years		—		—
Due after three years		893		902

Total debt securities	$	26,202	$	26,213

Auction Rate Securities

At December 31, 2011 and 2010, we held various auction rate securities with par values of $1.1 million and $2.2 million, respectively. The assets underlying the auction rate instruments were primarily municipal bonds and preferred closed end funds. Maturity dates for our auction rate securities range from 2030 to 2036. Since 2008, $16.6 million of the related securities were called at par by their issuers, including $25,000 in 2011 and $125,000 in auction rate securities redeemed in 2010. In 2011, we redeemed auction rate preferred securities with a par value of $1.1 million for $891,000.

At December 31, 2011, there was insufficient observable auction rate market information available to determine the fair value of most of our auction rate security investments. Therefore, we estimated fair value using a trinomial discount model employing assumptions that market participants would use in their estimates of fair value. Certain of these assumptions included financial standing of the issuer, final stated maturities, estimates of the probability of the issue being called prior to final maturity, estimates of the probability of defaults and recoveries, expected changes in interest rates paid on the securities, interest rates paid on similar instruments, and an estimated illiquidity discount due to extended redemption periods.

As a result of the failed auctions, our auction rate instruments are not currently liquid. Due to the continuation of the unstable credit environment, we believe that the recovery period for most of our auction rate instruments will exceed 12 months. Accordingly, we have classified the fair value of the auction rate instruments that have not been redeemed subsequent to December 31, 2011, as long-term.