Short-Term Borrowings and Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	0.80%
Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End	1.10%
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
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
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
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	$ 328	$ 322
Commercial Paper [Member]
Debt Instrument [Line Items]
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.30%