Postretirement Plans (Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 468	$ 411	$ 1,414	$ 1,233
Interest cost	713	751	2,175	2,253
Expected return on plan assets	(969)	(958)	(2,907)	(2,874)
Amortization of prior service costs	52	56	150	168
Recognized net actuarial loss	530	484	1,668	1,452
Settlement and curtailment loss/(gain)	84		104	10
Net periodic benefit cost	878	744	2,604	2,242
Net periodic benefit cost included in Earnings from operations	775	583	2,319	1,831
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	37	36	111	108
Interest cost	65	79	198	237
Expected return on plan assets	(1)	(2)	(5)	(6)
Amortization of prior service costs	(45)	(49)	(135)	(147)
Recognized net actuarial loss	24	30	72	90
Settlement and curtailment loss/(gain)				(2)
Net periodic benefit cost	80	94	241	280
Net periodic benefit cost included in Earnings from operations	$ 90	$ 132	$ 269	$ 414