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Pension And Postretirement Benefits (Fair Value Assets Measured On Recurring Basis Unobservable Input (Level 3) Reconciliation) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Pension Assets [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year $ 10,688 $ 11,465
Realized gains (losses) 870 1,543
Unrealized gains (losses) 3 (323)
Transfers in 19 22
Transfers out (19) (25)
Purchases 939 1,265
Sales (2,841) (3,259)
Balance, end of year 9,659 10,688
Pension Assets [Member] | Equities [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year 0 0
Realized gains (losses) (1) 0
Unrealized gains (losses) 1 0
Transfers in 0 0
Transfers out 0 0
Purchases 0 1
Sales 0 (1)
Balance, end of year 0 0
Pension Assets [Member] | Fixed Income Funds [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year 444 547
Realized gains (losses) 29 41
Unrealized gains (losses) (16) (1)
Transfers in 0 0
Transfers out 0 (3)
Purchases 29 55
Sales (110) (195)
Balance, end of year 376 444
Pension Assets [Member] | Private Equity Funds [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year 5,399 5,724
Realized gains (losses) 426 696
Unrealized gains (losses) 132 (76)
Transfers in 0 0
Transfers out (19) (22)
Purchases 436 531
Sales (1,448) (1,454)
Balance, end of year 4,926 5,399
Pension Assets [Member] | Real Estate And Real Assets [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year 4,845 5,194
Realized gains (losses) 416 806
Unrealized gains (losses) (114) (246)
Transfers in 19 22
Transfers out 0 0
Purchases 474 678
Sales (1,283) (1,609)
Balance, end of year 4,357 4,845
Postretirement Assets [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year 317 446
Realized gains (losses) (18) 42
Unrealized gains (losses) 23 (17)
Transfers in 40  
Transfers out (26) (1)
Purchases 31 6
Sales (115) (159)
Balance, end of year 252 317
Postretirement Assets [Member] | Fixed Income Funds [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year 3 26
Realized gains (losses) 0 0
Unrealized gains (losses) 0 1
Transfers in 15  
Transfers out (1) (1)
Purchases 0 0
Sales (1) (23)
Balance, end of year 16 3
Postretirement Assets [Member] | Private Equity Funds [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year 218 309
Realized gains (losses) (16) 45
Unrealized gains (losses) 24 (29)
Transfers in 0  
Transfers out 0 0
Purchases 30 6
Sales (101) (113)
Balance, end of year 155 218
Postretirement Assets [Member] | Real Assets [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Balance, beginning of year 96 111
Realized gains (losses) (2) (3)
Unrealized gains (losses) (1) 11
Transfers in 25  
Transfers out (25) 0
Purchases 1 0
Sales (13) (23)
Balance, end of year $ 81 $ 96