Postretirement Plans (Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 414	$ 473
Interest cost	784	731
Expected return on plan assets	(1,041)	(969)
Amortization of prior service costs	45	49
Recognized net actuarial loss	261	569
Settlement and curtailment loss	338	20
Net periodic benefit cost	801	873
Net periodic benefit cost included in Earnings from operations	1,035	791
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	32	37
Interest cost	72	67
Expected return on plan assets	(2)	(2)
Amortization of prior service costs	(36)	(45)
Recognized net actuarial loss	2	24
Settlement and curtailment loss
Net periodic benefit cost	68	81
Net periodic benefit cost included in Earnings from operations	$ 71	$ 91