Retirement Benefits (Unaudited) (Details 1) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Defined contribution plan, employer contributions	$ 87	$ 85
Pension Benefits
Components of Net Periodic Benefit Cost
Service cost	112	121
Interest cost	321	306
Expected return on plan assets	(463)	(494)
Amortization of:
Prior service credit	(15)	(15)
Net loss from previous years	178	171
Net periodic benefit cost	133	89
Defined Benefit Plan, Expected Contributions in Current Fiscal Year [Abstract]
Defined benefit plan, contributions by Employer	27	525
Medical and Life Benefits
Components of Net Periodic Benefit Cost
Service cost	8	9
Interest cost	24	24
Expected return on plan assets	(21)	(22)
Amortization of:
Prior service credit	(6)	(7)
Net loss from previous years	3	6
Net periodic benefit cost	8	10
Defined Benefit Plan, Expected Contributions in Current Fiscal Year [Abstract]
Defined benefit plan, contributions by Employer	$ 11	6
Voluntary Contributions [Member] | Pension Benefits
Defined Benefit Plan, Expected Contributions in Current Fiscal Year [Abstract]
Defined benefit plan, contributions by Employer		$ 500