Investments (Fair Values by Classification) (Details) - USD ($) $ in Millions |
Sep. 30, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Fair values of available-for-sale investments by classification in the Consolidated Balance Sheets | ||
| Marketable securities | $ 952 | $ 4,381 |
| Total interest-bearing securities | 12,275 | 9,845 |
| Available-for-sale investments [Member] | ||
| Fair values of available-for-sale investments by classification in the Consolidated Balance Sheets | ||
| Cash and cash equivalents | 11,323 | 5,464 |
| Marketable securities | 952 | 4,381 |
| Total interest-bearing securities | $ 12,275 | $ 9,845 |