Pension And Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ 1,888	$ 1,699	$ 432		$ (4,048)	$ 2,726
Pension Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate for determining projected benefit obligation	3.30%				3.30%			4.50%
Discount rate increase (decrease) during period	(0.40%)	(0.40%)	(0.40%)
Actual Long-term Rate of Return on Plan Assets					13.40%
Pension Benefit [Member] | Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected Long-term Rate of Return on Plan Assets							7.00%
Pension Benefit [Member] | Other Income (Expense) [Member]
Defined Benefit Plan Disclosure [Line Items]
Special termination benefits					$ 81
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ (29)
Net supplemental retirement pension benefits costs	$ 24			$ 24	$ 74	$ 65