Retirement Plans (Schedule of Annual Pension and Other Post-Retirement Benefit Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 245	$ 211	$ 203
Interest cost	517	509	491
Expected return on plan assets	(599)	(600)	(575)
Recognized net actuarial loss (gain)	173	87	35
Amortization of prior service (credit) cost	(43)	(41)	(46)
Annual benefit cost	293	166	108
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	13	10	8
Interest cost	62	59	64
Expected return on plan assets	(31)	(32)	(32)
Recognized net actuarial loss (gain)	4	(5)	(6)
Amortization of prior service (credit) cost	6	2	1
Annual benefit cost	$ 54	$ 34	$ 35