3. SECURITIES AVAILABLE FOR SALE

The amortized cost, gross unrealized gains and losses and estimated fair value of securities available for sale at December 31, 2011 and 2010 are summarized as follows (dollars in thousands):

The following table presents the amortized cost and estimated fair value of securities available for sale as of December 31, 2011, by contractual maturity (dollars in thousands). Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

Securities with an amortized cost of $172.1 million and $175.8 million as of December 31, 2011 and 2010, respectively, were pledged to secure public deposits, repurchase agreements and for other purposes. Sales, calls, maturities and paydowns of securities available for sale produced the following results for the years ended December 31, 2011, 2010 and 2009 (dollars in thousands):

The primary purpose of the investment portfolio is to generate income and meet liquidity needs of the Company through readily saleable financial instruments. The portfolio includes fixed rate bonds, whose prices move inversely with rates. At the end of any accounting period, the investment portfolio has unrealized gains and losses. The Company monitors the portfolio, which is subject to liquidity needs, market rate changes and credit risk changes, to see if adjustments are needed. The primary cause of temporary impairments was the increase in spreads over comparable Treasury bonds. As of December 31, 2011, there were $4.9 million, or 5 issues, of individual securities that had been in a continuous loss position for more than 12 months. These securities had an unrealized loss of $722,000 and consisted of municipal obligations and corporate bonds. As of December 31, 2010, there were $18.9 million, or 43 issues, of individual securities that had been in a continuous loss position for more than 12 months. These securities had an unrealized loss of $2.0 million and consisted primarily of municipal obligations and corporate bonds.

The Company recognizes an impairment is other-than-temporary if any of the following conditions exists: the entity intends to sell the security; it is more likely than not that the entity will be required to sell the security before recovery of its amortized cost basis; or the entity does not expect to recover the security's entire amortized cost basis (even if the entity does not intend to sell). If a credit loss exists, but an entity does not intend to sell the impaired debt security and is not more likely than not to be required to sell before recovery, the impairment is other-than-temporary and should be separated into a credit portion to be recognized in earnings and the remaining amount relating to all other factors recognized as other comprehensive loss.

During each quarter and at year end, the Company conducts an assessment of the securities portfolio for OTTI consideration. The Company determined that a single issuer Trust Preferred security incurred credit-related other than temporary impairment ("OTTI") of $400,000 during the year ended December 31, 2011. No OTTI was recognized in 2010 or 2009. There is a possibility that the Company will sell the security before recovering all unamortized costs. The significant inputs the Company considered in determining the amount of the credit loss are as follows:

OTTI recognized for the periods presented is summarized as follow (dollars in thousands):

The following tables present the gross unrealized losses and fair values as of December 31, 2011 and 2010, aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position (dollars in thousands):