Borrowing and Lines of Credit (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Line of Credit Facility [Line Items]
Maximum Commercial Paper Borrowing Authority	$ 5,000		$ 5,000
Aggregate Line of Credit Agreements, Maximum Borrowing Capacity	7,000		7,000
Borrowings outstanding	$ 0		0
Proceeds from Issuance of Debt			$ 0
Average Years of Maturity of Long Term Debt			14 years
Average interest expense rate	4.20%	3.80%	4.10%	3.80%
Debt Exchanged		$ 8,200		$ 8,200
5.0B Revolving Credit Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 5,000		$ 5,000
$2.0B May 6, 2020 revolving credit agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,000		$ 2,000