Postretirement Plans (Components of Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 473	$ 411	$ 946	$ 822
Interest cost	731	751	1,462	1,502
Expected return on plan assets	(969)	(958)	(1,938)	(1,916)
Amortization of prior service costs	49	56	98	112
Recognized net actuarial loss	569	484	1,138	968
Settlement and curtailment loss/(gain)		3	20	10
Net periodic benefit cost	853	747	1,726	1,498
Net periodic benefit cost included in Earnings from operations	753	593	1,544	1,248
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	37	36	74	72
Interest cost	66	79	133	158
Expected return on plan assets	(2)	(2)	(4)	(4)
Amortization of prior service costs	(45)	(49)	(90)	(98)
Recognized net actuarial loss	24	30	48	60
Settlement and curtailment loss/(gain)				(2)
Net periodic benefit cost	80	94	161	186
Net periodic benefit cost included in Earnings from operations	$ 88	$ 133	$ 179	$ 282