Derivative Financial Instruments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Collateral received	$ 22
Collateral posted		$ 1
Unrecognized losses for all terminated cash flow hedges included in accumulated other comprehensive loss	262	246
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	262	$ 246
Total amount of amortization over the next twelve months for all cash flow hedges	15
Cash Flow Hedging [Member] | Terminations [Domain]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	425
Cash Flow Hedging [Member] | Expired hedge [Domain]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Settlement amount	$ 35