Employee Postretirement Benefits (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Projected Benefit Obligation		$ 5,708,000,000	$ 5,187,000,000
Defined Benefit Plan, Health Care Capped And Indexed Annually Percent		3.00%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year		7.10%
Defined Benefit Plan, Health Care Cost Trend Rate Assumed For Fifth Succeeding Fiscal Year		5.10%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate	6.68%	7.35%	8.19%
Percentage of equity collars in place on equity allocation		33.00%
Equity collars on defined benefit plans		1,400,000,000
Defined Benefit Plan, Significant Concentrations of Risk		there were no significant concentrations of equity or debt securities in any single issuer or industry.
Transfers of assets, fair value determinations		0	0
Fair value of plan assets		4,840,000,000	4,192,000,000
United States [Member]
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Projected Benefit Obligation		4,021,000,000	3,744,000,000
Fair value of plan assets		3,478,000,000	2,984,000,000
Fair Value, Inputs, Level 3 [Member]
Fair value of plan assets		$ 1,000,000	$ 1,000,000
Minimum [Member]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year, Description		50000000
Maximum [Member]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year, Description		100000000