Retirement Plans (Fair Values Pension Plan Assets By Asset Class) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 8,735	$ 11,368	$ 10,312
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,120	3,807
Significant Observable Inputs (Level 2) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,969	3,146
Significant Unobservable Inputs (Level 3) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	111	29	(59)
Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,434	1,177
Alternative Investment	59	66
Corporate Bonds [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Corporate Bonds [Member] | Significant Observable Inputs (Level 2) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,434	1,177
Corporate Bonds [Member] | Significant Unobservable Inputs (Level 3) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,262	2,778
Government Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Government Securities [Member] | Significant Observable Inputs (Level 2) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	2,262	2,778
Government Securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	1
Mortgage Backed Securities [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Mortgage Backed Securities [Member] | Significant Observable Inputs (Level 2) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Mortgage Backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	1	1
Other Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	(723)	(802)
Alternative Investment	180	232
Other Fixed Income [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Other Fixed Income [Member] | Significant Observable Inputs (Level 2) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	(736)	(814)
Other Fixed Income [Member] | Significant Unobservable Inputs (Level 3) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	13	12	11
Derivatives [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	98	8
Derivatives [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Derivatives [Member] | Significant Observable Inputs (Level 2) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	(8)
Derivatives [Member] | Significant Unobservable Inputs (Level 3) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	98	16	$ (71)
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	294	397
Cash and Cash Equivalents [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	294	397
Cash and Cash Equivalents [Member] | Significant Observable Inputs (Level 2) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Cash and Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	685	1,291
Alternative Investment	515	708
Equity Securities, US [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	685	1,291
Equity Securities, US [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Equity Securities, US [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,150	2,132
Alternative Investment	433	866
Equity Securities, Non-US [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1,141	2,119
Equity Securities, Non-US [Member] | Significant Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	9	13
Equity Securities, Non-US [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0	0
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Alternative Investment	886	927
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Alternative Investment	518	481
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Alternative Investment	$ 944	$ 1,106