Pension and Other Postretirement Benefits - Plan Amendments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Mar. 31, 2013	Jun. 30, 2013	Jun. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Pre-tax curtailment gain or settlement loss		$ 19	$ (6)
After-tax curtailment gain or settlement loss		12	(4)
Increase (decrease) to shareholders' equity resulting from plan amendments	37
Retiree Health Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (decrease) to liability for defined benefit plans resulting from plan amendments	$ (57)

The amount of increase or decrease due to a change in the terms of an existing plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.

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+ Details

- Definition

Before tax amount of the income statement impact of the reclassification adjustment for prior service costs recognized as a component of net period benefit cost.

+ References

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+ Details

- Definition

Net of tax amount of the income statement impact of the reclassification adjustment for prior service costs recognized as a component of net period benefit cost.

+ References

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+ Details