Derivative Financial Instruments and Hedging Activities Derivative Financial Instruments and Hedging Activities (Schedule of Fair Value Hedging Basis Adjustments) (Details) - Designated as Hedging Instrument [Member] - Long-term Debt [Member] - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||
| Hedged Liability, Fair Value Hedge | $ (2,171) | $ (2,954) |
| Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease) | $ (64) | $ (49) |