Debt (Short Term Debt Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Short-term debt	$ 9,682,000,000	$ 11,428,000,000
Line of credit | Accounts receivable securitization facility expiring 2019
Short-term Debt [Line Items]
Short-term debt	634,000,000
Maximum borrowing capacity	$ 800,000,000
Extension period	364 days
Collateral amount	$ 922,000,000