Derivative Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Collateral received	$ 37	$ 22
Unrecognized losses for all terminated cash flow hedges included in accumulated other comprehensive loss	250	262
Cash Flow Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrecognized losses for all terminated cash flow hedges included in accumulated other comprehensive loss	250	$ 262
Total amount of amortization over the next twelve months for all cash flow hedges	14
Cash Flow Hedging [Member] | Terminations [Domain]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	$ 725