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] - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Debt Available-for-Sale Securities [Member] | ||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||
| Hedged Asset, Fair Value Hedge | $ 0 | $ 85 |
| Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease) | 0 | 0 |
| Long-term Debt [Member] | ||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||
| Hedged Liability, Fair Value Hedge | (2,954) | (3,103) |
| Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease) | $ (49) | $ 50 |