Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

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Subsequent Event (Details) - USD ($) $ in Millions	Apr. 06, 2020	Apr. 30, 2020	Apr. 21, 2020	Mar. 31, 2020	Dec. 31, 2019
Subsequent Events [Abstract]
Cash on hand				$ 7,123	$ 8,284
Credit Facility 1
Subsequent Event
Credit facilities				$ 10,500
Subsequent Event \| 10- and 30- year bond
Subsequent Event
Cash raised from bonds	$ 2,000
Subsequent Event \| 10 year bond
Subsequent Event
Bond term	10 years
Subsequent Event \| 30 year bond
Subsequent Event
Bond term	30 years
Subsequent Event \| Incremental short term credit facility
Subsequent Event
Credit facilities			$ 3,900
Subsequent Event \| Commercial paper under the commercial paper support programs in the U.S. and Canada [Member]
Subsequent Event
Credit facilities		$ 4,100