Financial Instruments (Marketable Equity Securities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	$ 6,900	$ 4,604
Equity securities	2,814	3,296
Marketable Securities	2,814	3,296
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	6,811	4,604
Equity securities	2,592	3,046
Marketable Securities	2,592	3,046
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	5,876	6,856
Money market funds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	6,806	4,604
Mutual funds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	89
Equity securities	222	$ 250
Equity Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	$ 5