Pension and Other Postemployment Benefits (Details 1) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pensions
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 161	$ 130	$ 99
Interest cost	389	374	314
Expected return on plan assets	(486)	(446)	(361)
Amortization of prior service cost	12	14	13
Other adjustments (settlements, curtailments, etc.)	0	6	0
Pensions & OPEB mark-to-market adjustment	735	729	264
Net periodic cost (credit)	811	807	329
OPEB
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	12	13	10
Interest cost	47	48	45
Expected return on plan assets	(37)	(40)	(36)
Amortization of prior service cost	(203)	(203)	(193)
Other adjustments (settlements, curtailments, etc.)	0	0	0
Pensions & OPEB mark-to-market adjustment	140	36	22
Net periodic cost (credit)	$ (41)	$ (146)	$ (152)