Comprehensive Income (Loss) (Reclassification Out Of Accumulated Other Comprehensive) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Benefits [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax			$ (208)	$ (21)
Postretirement Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, net of tax			5	4
Reclassification out of Accumulated Other Comprehensive Loss [Member] | Pension Benefits [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	$ (147)	$ (14)	(267)	(28)
Tax impact	29	3	59	7
Reclassifications, net of tax	(118)	(11)	(208)	(21)
Reclassification out of Accumulated Other Comprehensive Loss [Member] | Pension Benefits [Member] | Actuarial Gains (Losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	(30)	(14)	(47)	(28)
Reclassification out of Accumulated Other Comprehensive Loss [Member] | Pension Benefits [Member] | One-Time Gain (Loss) On disposal [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	(61)		(61)
Reclassification out of Accumulated Other Comprehensive Loss [Member] | Pension Benefits [Member] | Pension Settlement Cost [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	(56)		(159)
Reclassification out of Accumulated Other Comprehensive Loss [Member] | Postretirement Costs [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax		3	6	6
Tax impact		(1)	(1)	(2)
Reclassifications, net of tax		2	5	4
Reclassification out of Accumulated Other Comprehensive Loss [Member] | Postretirement Costs [Member] | Prior-Service Credits (Costs) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	8	$ 3	16	4
Reclassification out of Accumulated Other Comprehensive Loss [Member] | Postretirement Costs [Member] | Actuarial Gains (Losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	(1)		(3)	$ 2
Reclassification out of Accumulated Other Comprehensive Loss [Member] | Postretirement Costs [Member] | One-Time Gain (Loss) On disposal [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, pretax	$ (7)		$ (7)