These excerpts taken from the RIG 10-K filed Feb 26, 2009.
Cash and cash equivalents—Cash equivalents are highly liquid debt instruments with an original maturity of three months or less and may consist of time deposits with a number of commercial banks with high credit ratings, Eurodollar time deposits, certificates of deposit and commercial paper. We may also invest excess funds in no-load, open-end, management investment trusts ("management trusts"). The management trusts invest exclusively in high quality money market instruments. Cash equivalents are stated at cost plus accrued interest, which approximates fair value. We record restricted cash in other assets in our consolidated balance sheet. At December 31, 2008 and 2007, we had $8 million and $7 million, respectively, classified as restricted cash related to collateral for surety bonds to satisfy certain Venezuelan tax requirements.
Cash and cash equivalents—The carrying amounts approximate fair value because of the short maturity of those instruments.