Postretirement Plans (Components of Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 473	$ 411
Interest cost	731	751
Expected return on plan assets	(969)	(958)
Amortization of prior service costs	49	56
Recognized net actuarial loss	569	484
Settlement and curtailment loss/(gain)	20	7
Net periodic benefit cost	873	751
Net periodic benefit cost included in Earnings from operations	791	655
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	37	36
Interest cost	67	79
Expected return on plan assets	(2)	(2)
Amortization of prior service costs	(45)	(49)
Recognized net actuarial loss	24	30
Settlement and curtailment loss/(gain)		(2)
Net periodic benefit cost	81	92
Net periodic benefit cost included in Earnings from operations	$ 91	$ 149