Postretirement Plans (Reconciliation Of Level 3 Assets Held) (Details) - Pension Plans [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		$ 56,692	$ 56,514
Net Realized and Unrealized Gains/(Losses)		8,552	3,885
Net Purchases, Issuances and Settlements		(744)	(24)
Ending balance at fair value		64,011	56,692
Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		350	464
Net Realized and Unrealized Gains/(Losses)		9	4
Net Purchases, Issuances and Settlements		(40)	(97)
Net Transfers Into/(Out of) Level 3		(4)	(21)
Ending balance at fair value		315	350
Fixed Income Securities [Member] | Corporate [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		16,730
Ending balance at fair value		19,603	16,730
Fixed Income Securities [Member] | Corporate [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value	[1]	12
Net Purchases, Issuances and Settlements	[1]	1
Net Transfers Into/(Out of) Level 3	[1]	(1)
Ending balance at fair value	[1]	12	12
Fixed Income Securities [Member] | US Treasury and Government [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		4,876
Ending balance at fair value		5,430	4,876
Fixed Income Securities [Member] | US Treasury and Government [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		1	1
Net Transfers Into/(Out of) Level 3		(1)
Ending balance at fair value			1
Fixed Income Securities [Member] | Mortgage backed, asset back, and other securities [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Ending balance at fair value		760
Fixed Income Securities [Member] | Mortgage backed, asset back, and other securities [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value	[1]	331
Net Realized and Unrealized Gains/(Losses)	[1]	10
Net Purchases, Issuances and Settlements	[1]	(39)
Net Transfers Into/(Out of) Level 3	[1]	(2)
Ending balance at fair value	[1]	300	331
Fixed Income Securities [Member] | Mortgage backed and asset backed
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		706
Ending balance at fair value			706
Fixed Income Securities [Member] | Mortgage backed and asset backed | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value	[1]	336	440
Net Realized and Unrealized Gains/(Losses)	[1]		7
Net Purchases, Issuances and Settlements	[1]		(93)
Net Transfers Into/(Out of) Level 3	[1]		(18)
Ending balance at fair value	[1]		336
Fixed Income Securities [Member] | Corporate and other [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value	[1]	7	11
Net Purchases, Issuances and Settlements	[1]		(1)
Net Transfers Into/(Out of) Level 3	[1]		(3)
Ending balance at fair value	[1]		7
Fixed Income Securities [Member] | Other Debt Obligations [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		74
Ending balance at fair value		118	74
Equity securities [Member] | United States Common And Preferred Stock [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		5,374
Ending balance at fair value		4,615	5,374
Equity securities [Member] | United States Common And Preferred Stock [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		1	1
Net Realized and Unrealized Gains/(Losses)		(1)
Ending balance at fair value			1
Equity securities [Member] | Non United States Common And Preferred Stock [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		5,746
Ending balance at fair value		6,204	5,746
Equity securities [Member] | Non United States Common And Preferred Stock [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value			2
Net Purchases, Issuances and Settlements			(2)
Private Equity Funds [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value			3
Net Realized and Unrealized Gains/(Losses)			(3)
Real estate and real assets [Member] | Real assets [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		672
Ending balance at fair value		705	672
Real estate and real assets [Member] | Real assets [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		5	6
Net Purchases, Issuances and Settlements		(2)	(1)
Ending balance at fair value		$ 3	$ 5

[1] Certain fixed income securities were reclassified between mortgage backed and asset backed to corporate on January 1, 2017 and 2016.