Cash and cash equivalents primarily consist of deposits held at major banks, money market funds, Tier-1 commercial paper, U.S. Treasury obligations, U.S. government agency and government sponsored enterprise obligations, and other securities with original maturities of 90 days or less. Marketable securities primarily consist of time deposits held at major banks, Tier-1 commercial paper, corporate notes, U.S. Treasury obligations and U.S. government agency and government sponsored enterprise debt obligations and certain other securities.

The amortized principal amounts of our cash, cash equivalents and marketable securities approximated their fair values at May 31, 2011 and 2010. We use the specific identification method to determine any realized gains or losses from the sale of our marketable securities classified as available-for-sale. Such realized gains and losses were insignificant for fiscal 2011, 2010 and 2009. The following table summarizes the components of our cash equivalents and marketable securities held, substantially all of which were classified as available-for-sale:


	May 31,
(in millions)	2011		2010
Money market funds	$	3,362	$	2,423
U.S. Treasury, U.S. government and U.S. government agency debt securities		1,150		3,010
Commercial paper, corporate debt securities and other		13,875		5,634

Total investments	$	18,387	$	11,067

Investments classified as cash equivalents	$	5,702	$	2,512

Investments classified as marketable securities	$	12,685	$	8,555

Substantially all of our marketable security investments held as of May 31, 2011 mature within one year. Our investment portfolio is subject to market risk due to changes in interest rates. As described above, we place our investments with high credit quality issuers and, by policy, limit the amount of credit exposure to any one issuer. As stated in our investment policy, we are averse to principal loss and seek to preserve our invested funds by limiting default risk, market risk and reinvestment risk.