Retirement Plans (Schedule of Annual Pension and Other Post-Retirement Benefit Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 298	$ 266	$ 245
Interest cost	492	523	517
Expected return on plan assets	(590)	(588)	(599)
Recognized net actuarial loss (gain)	409	287	173
Amortization of prior service (credit) cost	(67)	(42)	(43)
Net periodic cost	542	446	293
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	15	12	13
Interest cost	53	59	62
Expected return on plan assets	(29)	(30)	(31)
Recognized net actuarial loss (gain)	26	10	4
Amortization of prior service (credit) cost	7	7	6
Net periodic cost	$ 72	$ 58	$ 54