v3.3.1.900
Retirement Benefits Plans Retirement Benefits Plans - Change in Plan Level 3 Assets (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value $ 185 $ 120 $ 100
Gains (losses) relating to Level 3 assets still held at year-end (6) (2)  
Defined Benefit Plan, Purchases, Sales, and Settlements 80 53  
Defined Benefit Plan, Transfers Between Measurement Levels (9) (31)  
Real Estate Funds [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value 7 6 6
Gains (losses) relating to Level 3 assets still held at year-end 1 0  
Defined Benefit Plan, Purchases, Sales, and Settlements 0 0  
Defined Benefit Plan, Transfers Between Measurement Levels 0 0  
Hedge Funds [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value 92 54 0
Gains (losses) relating to Level 3 assets still held at year-end (5) 1  
Defined Benefit Plan, Purchases, Sales, and Settlements 43 53  
Defined Benefit Plan, Transfers Between Measurement Levels 0 0  
Other Pension Plan Assets [Member]      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value 86 60 $ 94
Gains (losses) relating to Level 3 assets still held at year-end (2) (3)  
Defined Benefit Plan, Purchases, Sales, and Settlements 37 0  
Defined Benefit Plan, Transfers Between Measurement Levels $ (9) $ (31)