The following table provides the cost and fair value for the major categories of securities available for sale carried at fair value. The net unrealized gains (losses) are reported on an after-tax basis as a component of cumulative OCI. There were no securities classified as held to maturity as of the periods presented.

• Includes collateralized loan obligations with a cost basis and fair value of $8.5 billion and $8.6 billion, respectively, at March 31, 2012, and $8.1 billion for both cost basis and fair value, at December 31, 2011.
• Included in the “Other” category are asset-backed securities collateralized by auto leases or loans and cash reserves with a cost basis and fair value of $6.9 billion and $7.0 billion, respectively, at March 31, 2012, and $6.7 billion and $6.7 billion, respectively, at December 31, 2011. Also included in the "Other" category are asset-backed securities collateralized by home equity loans with a cost basis and fair value of $829 million and $955 million, respectively, at March 31, 2012, and $846 million and $932 million, respectively, at December 31, 2011. The remaining balances primarily include asset-backed securities collateralized by credit cards and student loans.

Gross Unrealized Losses and Fair Value

The following table shows the gross unrealized losses and fair value of securities in the securities available-for-sale portfolio by length of time that individual securities in each category had been in a continuous loss position. Debt securities on which we have taken credit-related OTTI write-downs are categorized as being “less than 12 months” or “12 months or more” in a continuous loss position based on the point in time that the fair value declined to below the cost basis and not the period of time since the credit-related OTTI write-down.

We do not have the intent to sell any securities included in the previous table. For debt securities included in the table, we have concluded it is more likely than not that we will not be required to sell prior to recovery of the amortized cost basis. We have assessed each security with gross unrealized losses for credit impairment. For debt securities, we evaluate, where necessary, whether credit impairment exists by comparing the present value of the expected cash flows to the securities' amortized cost basis. For equity securities, we consider numerous factors in determining whether impairment exists, including our intent and ability to hold the securities for a period of time sufficient to recover the cost basis of the securities.

       For complete descriptions of the factors we consider when analyzing debt securities for impairment, see Note 5 in our 2011 Form 10-K. There have been no material changes to our methodologies for assessing impairment in first quarter 2012.

Securities of U.S. Treasury and federal agencies and federal agency mortgage-backed securities (MBS) The unrealized losses associated with U.S. Treasury and federal agency securities and federal agency MBS are primarily driven by changes in interest rates and not due to credit losses given the explicit or implicit guarantees provided by the U.S. government.

Securities of U.S. states and political subdivisions The unrealized losses associated with securities of U.S. states and political subdivisions are primarily driven by changes in interest rates and not due to the credit quality of the securities. Substantially all of these investments are investment grade. The securities were generally underwritten in accordance with our own investment standards prior to the decision to purchase. Some of these securities are guaranteed by a bond insurer, but we did not rely on this guarantee in making our investment decision. These investments will continue to be monitored as part of our ongoing impairment analysis, but are expected to perform, even if the rating agencies reduce the credit rating of the bond insurers. As a result, we expect to recover the entire amortized cost basis of these securities.

Residential and commercial MBS The unrealized losses associated with private residential MBS and commercial MBS are primarily driven by changes in projected collateral losses, credit spreads and interest rates. We assess for credit impairment by estimating the present value of expected cash flows. The key assumptions for determining expected cash flows include default rates, loss severities and/or prepayment rates. We estimate losses to a security by forecasting the underlying mortgage loans in each transaction. We use forecasted loan performance to project cash flows to the various tranches in the structure. We also consider cash flow forecasts and, as applicable, independent industry analyst reports and forecasts, sector credit ratings, and other independent market data. Based upon our assessment of the expected credit losses and the credit enhancement level of the securities, we expect to recover the entire amortized cost basis of these securities.

Corporate Debt Securities The unrealized losses associated with corporate debt securities are primarily related to unsecured debt obligations issued by various corporations. We evaluate the financial performance of each issuer on a quarterly basis to determine that the issuer can make all contractual principal and interest payments. Based upon this assessment, we expect to recover the entire amortized cost basis of these securities.

Collateralized Debt Obligations (CDOs) The unrealized losses associated with CDOs relate to securities primarily backed by commercial, residential or other consumer collateral. The unrealized losses are primarily driven by changes in projected collateral losses, credit spreads and interest rates. We assess for credit impairment by estimating the present value of expected cash flows. The key assumptions for determining expected cash flows include default rates, loss severities and prepayment rates. We also consider cash flow forecasts and, as applicable, independent industry analyst reports and forecasts, sector credit ratings, and other independent market data. Based upon our assessment of the expected credit losses and the credit enhancement level of the securities, we expect to recover the entire amortized cost basis of these securities.

Other Debt Securities The unrealized losses associated with other debt securities primarily relate to other asset-backed securities. The losses are primarily driven by changes in projected collateral losses, credit spreads and interest rates. We assess for credit impairment by estimating the present value of expected cash flows. The key assumptions for determining expected cash flows include default rates, loss severities and prepayment rates. Based upon our assessment of the expected credit losses and the credit enhancement level of the securities, we expect to recover the entire amortized cost basis of these securities.

Marketable Equity Securities Our marketable equity securities include investments in perpetual preferred securities, which provide very attractive tax-equivalent yields. We evaluated these hybrid financial instruments with investment-grade ratings for impairment using an evaluation methodology similar to that used for debt securities. Perpetual preferred securities are not considered to be other-than-temporarily impaired if there is no evidence of credit deterioration or investment rating downgrades of any issuers to below investment grade, and we expect to continue to receive full contractual payments. We will continue to evaluate the prospects for these securities for recovery in their market value in accordance with our policy for estimating OTTI. We have recorded impairment write-downs on perpetual preferred securities where there was evidence of credit deterioration.

OTHER SECURITIES AVAILABLE FOR SALE MATTERS The fair values of our investment securities could decline in the future if the underlying performance of the collateral for the residential and commercial MBS or other securities deteriorate and our credit enhancement levels do not provide sufficient protection to our contractual principal and interest. As a result, there is a risk that significant OTTI may occur in the future.

       The following table shows the gross unrealized losses and fair value of debt and perpetual preferred securities available for sale by those rated investment grade and those rated less than investment grade, according to their lowest credit rating by Standard & Poor's Rating Services (S&P) or Moody's Investors Service (Moody's). Credit ratings express opinions about the credit quality of a security. Securities rated investment grade, that is those rated BBB- or higher by S&P or Baa3 or higher by Moody's, are generally considered by the rating agencies and market participants to be low credit risk. Conversely, securities rated below investment grade, labeled as “speculative grade” by the rating agencies, are considered to be distinctively higher credit risk than investment grade securities. We have also included securities not rated by S&P or Moody's in the table below based on the internal credit grade of the securities (used for credit risk management purposes) equivalent to the credit rating assigned by major credit agencies. The unrealized losses and fair value of unrated securities categorized as investment grade based on internal credit grades were $128 million and $1.8 billion, respectively, at March 31, 2012, and $207 million and $6.2 billion, respectively, at December 31, 2011. If an internal credit grade was not assigned, we categorized the security as non-investment grade.

Contractual Maturities

The following table shows the remaining contractual maturities and contractual yields of debt securities available for sale. The remaining contractual principal maturities for MBS do not consider prepayments. Remaining expected maturities will differ from contractual maturities because borrowers may have the right to prepay obligations before the underlying mortgages mature.

Realized Gains and Losses

The following table shows the gross realized gains and losses on sales and OTTI write-downs related to the securities available-for-sale portfolio, which includes marketable equity securities, as well as net realized gains and losses on nonmarketable equity securities (see Note 6 – Other Assets).

Other-Than-Temporary Impairment

The following table shows the detail of total OTTI write-downs included in earnings for debt securities and marketable and nonmarketable equity securities.

Other-Than-Temporarily Impaired Debt Securities

The following table shows the detail of OTTI write-downs on debt securities available for sale included in earnings and the related changes in OCI for the same securities.

• Represents amounts recorded to OCI on debt securities in periods OTTI write-downs have occurred. Changes in fair value in subsequent periods on such securities, to the extent additional credit-related OTTI did not occur, are not reflected in this total. Increases represent OTTI write-downs recorded to OCI on debt securities in the periods non-credit related impairment has occurred. Decreases represent partial recoveries in the fair value of securities due to factors other than credit, where the increase in fair value was not sufficient to recover the full amount of the unrealized loss on such securities.

The following table presents a rollforward of the credit loss component recognized in earnings for debt securities we still own (referred to as “credit-impaired” debt securities). The credit loss component of the amortized cost represents the difference between the present value of expected future cash flows discounted using the security's current effective interest rate and the amortized cost basis of the security prior to considering credit losses. OTTI recognized in earnings for credit-impaired debt securities is presented as additions and is classified into one of two components based upon whether the current period is the first time the debt security was credit-impaired (initial credit impairment) or if the debt security was previously credit-impaired (subsequent credit impairments). The credit loss component is reduced if we sell, intend to sell or believe we will be required to sell previously credit-impaired debt securities. Additionally, the credit loss component is reduced if we receive or expect to receive cash flows in excess of what we previously expected to receive over the remaining life of the credit-impaired debt security, the security matures or is fully written down.

       Changes in the credit loss component of credit-impaired debt securities that we do not intend to sell were:

• Recoveries of previous credit impairments result from increases in expected cash flows subsequent to credit loss recognition. Such recoveries are reflected prospectively as interest yield adjustments using the effective interest method.

To determine credit impairment losses for asset-backed securities (e.g., residential MBS), we estimate expected future cash flows of the security by estimating the expected future cash flows of the underlying collateral and applying those collateral cash flows, together with any credit enhancements such as subordinated interests owned by third parties, to the security. The expected future cash flows of the underlying collateral are determined using the remaining contractual cash flows adjusted for future expected credit losses (which consider current delinquencies and nonperforming assets (NPAs), future expected default rates and collateral value by vintage and geographic region) and prepayments. The expected cash flows of the security are then discounted at the security's current effective interest rate to arrive at a present value amount. Total credit impairment losses on residential MBS that we do not intend to sell are shown in the table below. The table also presents a summary of the significant inputs considered in determining the measurement of the credit loss component recognized in earnings for residential MBS.

• Represents future expected credit losses on underlying pool of loans expressed as a percentage of total current outstanding loan balance.
• Represents the range of inputs/assumptions based upon the individual securities within each category.
• Represents distribution of credit impairment losses recognized in earnings categorized based on range of expected remaining life of loan losses. For example, 46% of credit impairment losses recognized in earnings for the quarter ended March 31, 2012, had expected remaining life of loan loss assumptions of 0 to 10%.
• Calculated by weighting the relevant input/assumption for each individual security by current outstanding amortized cost basis of the security.
• Represents current level of credit protection (subordination) for the securities, expressed as a percentage of total current underlying loan balance.
• Constant prepayment rate.