Postretirement Plans (Reconciliation Of Level 3 Assets Held) (Details) - Pension Plans [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		$ 56,514		$ 61,119
Net Realized and Unrealized Gains/(Losses)		3,885		(701)
Net Purchases, Issuances and Settlements		(24)		(649)
Ending balance at fair value		56,692		56,514
Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		464		621
Net Realized and Unrealized Gains/(Losses)		4		(12)
Net Purchases, Issuances and Settlements		(97)		(153)
Net Transfers Into/(Out of) Level 3		(21)		8
Ending balance at fair value		350		464
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		16,339
Ending balance at fair value		16,730		16,339
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]	11
Net Purchases, Issuances and Settlements		(1)
Net Transfers Into/(Out of) Level 3		(3)
Ending balance at fair value		7		11	[1]
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		4,801
Ending balance at fair value		4,876		4,801
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]	1	[2]
Ending balance at fair value		1		1	[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		706
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]	440
Net Realized and Unrealized Gains/(Losses)		7
Net Purchases, Issuances and Settlements		(93)
Net Transfers Into/(Out of) Level 3		(18)
Ending balance at fair value		336		440	[1]
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		830
Ending balance at fair value				830
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		448		611	[2]
Net Realized and Unrealized Gains/(Losses)				(9)
Net Purchases, Issuances and Settlements				(157)
Net Transfers Into/(Out of) Level 3				3
Ending balance at fair value				448
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		3		1	[2]
Net Purchases, Issuances and Settlements				1
Net Transfers Into/(Out of) Level 3				1
Ending balance at fair value				3
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		83
Ending balance at fair value		74		83
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		5,165
Ending balance at fair value		5,374		5,165
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
Net Transfers Into/(Out of) Level 3				1
Ending balance at fair value		1		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		5,712
Ending balance at fair value		5,746		5,712
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		1
Net Purchases, Issuances and Settlements		(2)		(2)
Net Transfers Into/(Out of) Level 3				3
Ending balance at fair value		0		2
Private Equity Funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		3
Ending balance at fair value		0		3
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		3
Net Realized and Unrealized Gains/(Losses)		(3)
Ending balance at fair value		0		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		632
Ending balance at fair value		672		632
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		6		4
Net Purchases, Issuances and Settlements		(1)		2
Ending balance at fair value		5		6
Other Debt Obligations [Member] | Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Beginning balance at fair value		$ 0
Net Realized and Unrealized Gains/(Losses)				(3)
Net Purchases, Issuances and Settlements				3
Ending balance at fair value				$ 0

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

[2] Certain fixed income securities were reclassified from corporate and mortgage backed and asset backed to U.S. government and agencies on January 1, 2015.