Employee Postretirement Benefits (Principal Plans and All Other Pension Plans) (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Projected benefit obligation (PBO)	$ 5,708,000,000	$ 5,187,000,000
Accumulated benefit obligation (ABO)	5,664,000,000	5,076,000,000
Fair value of plan assets, end of year	4,840,000,000	4,192,000,000
Principal Plans [Member]
Projected benefit obligation (PBO)	5,421,000,000	5,149,000,000
Accumulated benefit obligation (ABO)	5,395,000,000	5,041,000,000
Fair value of plan assets, end of year	4,840,000,000	4,192,000,000
Defined Benefit Pension [Member]
Projected benefit obligation (PBO)	5,920,000,000	5,658,000,000
Accumulated benefit obligation (ABO)	5,814,000,000	5,475,000,000
Fair value of plan assets, end of year	5,214,000,000	4,600,000,000	4,244,000,000
All Other Pension Plans [Member]
Projected benefit obligation (PBO)	499,000,000	509,000,000
Accumulated benefit obligation (ABO)	419,000,000	434,000,000
Fair value of plan assets, end of year	$ 374,000,000	$ 408,000,000

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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If aggregate disclosures are presented, the aggregate pension accumulated benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

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- Definition

If aggregate disclosures are presented, the aggregate projected benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented.

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