Financing (Commercial Paper Program And Credit Facilities) (Narrative) (Details) - USD ($)	Dec. 31, 2016	Jul. 10, 2015	Oct. 24, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Long-term debt	$ 12,269,000,000			$ 12,870,400,000
Credit facilities, borrowings outstanding	$ 0
Commercial paper
Line of Credit Facility [Line Items]
Long-term debt weighted average interest rate	0.30%
Long-term debt weighted average maturity	37 days
Long-term debt	$ 4,000,000,000
Revolving credit facility
Line of Credit Facility [Line Items]
Consolidated leverage ratio	0.65
Revolving credit facility | Federal funds rate
Line of Credit Facility [Line Items]
Basis spread percentage to determine floating interest rate	0.50%
Revolving credit facility | LIBOR-based rate
Line of Credit Facility [Line Items]
Basis spread percentage to determine floating interest rate	1.00%
Revolving credit facility | 5-Year Credit Facility | Long-term debt
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity				$ 4,000,000,000
Debt instrument, extension option, term		1 year
Revolving credit facility | 364-Day Facility | Short-term debt
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity		$ 7,000,000,000	$ 3,000,000,000
Line of credit, maximum outstanding during period		$ 0