Retirement Plans (Schedule of Annual Pension and Other Post-Retirement Benefit Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 266	$ 245	$ 211
Interest cost	523	517	509
Expected return on plan assets	(588)	(599)	(600)
Recognized net actuarial loss (gain)	287	173	87
Amortization of prior service (credit) cost	(42)	(43)	(41)
Net periodic cost	446	293	166
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	12	13	10
Interest cost	59	62	59
Expected return on plan assets	(30)	(31)	(32)
Recognized net actuarial loss (gain)	10	4	(5)
Amortization of prior service (credit) cost	7	6	2
Net periodic cost	$ 58	$ 54	$ 34