Financial Instruments (Marketable Equity Securities) (Details) - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Cash and Cash Equivalents | $ 4,604 | $ 3,493 |
| Equity securities | 3,296 | 1,222 |
| Marketable Securities | 3,296 | 1,222 |
| Level 1 | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Cash and Cash Equivalents | 4,604 | 3,493 |
| Equity securities | 3,046 | 994 |
| Marketable Securities | 3,046 | 994 |
| Level 2 | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Cash and Cash Equivalents | 6,856 | 5,963 |
| Money market funds | Level 1 | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Cash and Cash Equivalents | 4,604 | 3,493 |
| Mutual funds | Level 2 | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| Equity securities | $ 250 | $ 228 |