Financial Instruments (Marketable Equity Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	$ 12,210	$ 4,604
Marketable Equity Securities	5,858	3,296
Marketable Securities	5,858	3,296
Level 1:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	12,210	4,604
Marketable Equity Securities	5,470	3,046
Marketable Securities	5,470	3,046
Level 2:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	6,099	6,856
Money market funds | Level 1:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	12,210	4,604
Mutual funds | Level 2:
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable Equity Securities	$ 388	$ 250