The amortized cost, gross unrealized gains and losses, and fair value of securities available for sale and securities held to maturity are as follows:

A summary of securities with unrealized losses, aggregated by category and period of continuous unrealized loss, is as follows:

Unrealized losses in securities available for sale of $88 million as of September 30, 2012, were concentrated in non-agency residential mortgage-backed securities. Included in non-agency residential mortgage-backed securities are securities collateralized by loans that are considered to be “Prime” (defined as loans to borrowers with a Fair Isaac Corporation credit score of 620 or higher at origination), and “Alt-A” (defined as Prime loans with reduced documentation at origination). At September 30, 2012, the amortized cost and fair value of Alt-A residential mortgage-backed securities were $326 million and $280 million, respectively.

Certain Alt-A and Prime residential mortgage-backed securities experienced continued credit deterioration in the first nine months of 2012, including increased payment delinquency rates and losses on foreclosures of underlying mortgages. In addition, the Company increased the projected default rates for modified loans in the first quarter of 2012. Based on the Company’s cash flow projections, management determined that it does not expect to recover all of the amortized cost of these securities and therefore determined that these securities were other-than-temporarily impaired (OTTI). The Company employs a buy and hold strategy relative to its mortgage-related securities, and does not intend to sell these securities and will not be required to sell these securities before anticipated recovery of the unrealized losses on these securities. Further, the Company has adequate liquidity at September 30, 2012, with cash and cash equivalents totaling $8.5 billion, a loan-to-deposit ratio of 15%, adequate access to short-term borrowing facilities and regulatory capital ratios in excess of “well capitalized” levels. Because the Company does not intend to sell these securities and it is not “more likely than not” that the Company will be required to sell these securities, the Company recognized an impairment charge equal to the securities’ expected credit losses of $3 million and $28 million during the third quarter and first nine months of 2012, respectively. The expected credit losses were measured as the difference between the present value of expected cash flows and the amortized cost of the securities. Further deterioration in the performance of the underlying loans in the Company’s residential mortgage-backed securities portfolio could result in the recognition of additional impairment charges.

Actual credit losses on the Company’s residential mortgage-backed securities were not material during the third quarters or first nine months of 2012 or 2011.

The following table is a rollforward of the amount of credit losses recognized in earnings for OTTI securities held by the Company during the period for which a portion of the impairment was recognized in other comprehensive income:

The maturities of securities available for sale and securities held to maturity at September 30, 2012, are as follows:

Proceeds and gross realized gains (losses) from sales of securities available for sale are as follows: