Derivative Financial Instruments Derivative Financial Instruments (Fair Value Hedges, Financial Position) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Long term debt, current maturities [Domain]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Amount of Hedged Item	$ 700	$ 1,598
Cumulative basis adjustments for fair value hedges	37	22
Long-term Debt [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Amount of Hedged Item	19,335	17,787
Cumulative basis adjustments for fair value hedges	$ 0	$ (1)