Short-Term Borrowings and Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Bank credit facilities	$ 10,000	$ 0
Five year $4.4 billion credit facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit, Credit Facility, Maximum Borrowing Capacity	4,400
Bank credit facilities	$ 1,800
Line of Credit Facility, Interest Rate at Period End	1.60%
Line of Credit Facility, Expiration Period	5 years
Three year $4.4 billion credit facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit, Credit Facility, Maximum Borrowing Capacity	$ 4,400
Bank credit facilities	$ 4,400
Line of Credit Facility, Interest Rate at Period End	1.60%
Line of Credit Facility, Expiration Period	3 years
364 day $3.8 billion credit facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit, Credit Facility, Maximum Borrowing Capacity	$ 3,800
Bank credit facilities	$ 3,800
Line of Credit Facility, Interest Rate at Period End	1.70%
Line of Credit Facility, Expiration Period	364 days
Subsidiaries [Member]
Debt Instrument [Line Items]
Other Long-term Debt	$ 1,100	1,200
Other Long-term Debt, Current	$ 309	$ 322
Commercial Paper [Member]
Debt Instrument [Line Items]
Short-term Debt, Weighted Average Interest Rate, at Point in Time	2.40%