CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES

12 Months Ended

May 31, 2016

Cash, Cash Equivalents and Marketable Securities [Abstract]

CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES

3. CASH, CASH EQUIVALENTS AND MARKETABLE SECURITIES

Cash and cash equivalents primarily consist of deposits held at major banks, Tier-1 commercial paper and other securities with original maturities of 90 days or less. Marketable securities consist of Tier-1 commercial paper debt securities, corporate debt securities and certain other securities.

The amortized principal amounts of our cash, cash equivalents and marketable securities approximated their fair values at May 31, 2016 and 2015. 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 2016, 2015 and 2014. 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)	2016		2015
Money market funds	$	3,750	$	—
U.S. Treasury securities		214		668
Commercial paper debt securities		2,155		9,203
Corporate debt securities and other		35,274		28,844
Total investments	$	41,393	$	38,715
Investments classified as cash equivalents	$	5,420	$	6,063
Investments classified as marketable securities	$	35,973	$	32,652

As of each of May 31, 2016 and 2015, approximately 28% of our marketable securities investments mature within one year and 72% mature within one to six years. Our investment portfolio is subject to market risk due to changes in interest rates. As described above, we limit purchases of marketable debt securities to investment-grade securities, which have high credit ratings and also 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 and market risk.