Note 3.    Cash and Investments

Cash, cash equivalents, and marketable securities consisted of the following (in millions):

The following tables summarize unrealized gains and losses related to our investments in marketable securities designated as available-for-sale (in millions):

Gross unrealized gains and losses on cash equivalents were not material at December 31, 2010 and December 31, 2011.

We recognized gross realized gains of $212 million and $381 million for the years ended December 31, 2010 and 2011. We recognized gross realized losses of $27 million and $127 million for the years ended December 31, 2010 and 2011. We determine realized gains or losses on the sale of marketable securities on a specific identification method, and we reflect such gains and losses as a component of interest and other income, net, in our accompanying Consolidated Statements of Income.

The following table summarizes the estimated fair value of our investments in marketable securities, excluding the marketable equity securities, designated as available-for-sale and classified by the contractual maturity date of the securities (in millions):

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

As of December 31, 2010, we did not have any investments in marketable securities that were in an unrealized loss position for 12 months or greater.

During the fourth quarter of 2011, we recorded an other-than-temporary impairment charge of $88 million related to our investment in Clearwire Corporation. This amount was included in interest and other income, net in the accompanying Consolidated Statement of Income.

Securities Lending Program

From time to time, we enter into securities lending agreements with financial institutions to enhance investment income. We loan selected securities which are secured by collateral in the form of cash or securities. Cash collateral is invested in reverse repurchase agreements. We classify loaned securities as cash equivalents or marketable securities on the accompanying Consolidated Balance Sheets. We record the cash collateral as an asset with a corresponding liability. We classify reverse repurchase agreements maturing within three months as cash equivalents and those longer than three months as receivable under reverse repurchase agreements on the accompanying Consolidated Balance Sheets. For lending agreements collateralized by securities, we do not record an asset or liability as we are not permitted to sell or repledge the associated collateral.