Benefit Plans - Costs of Benefit Plans (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Other pension information
Income tax expense due to patient protection and affordable care act	$ 0	$ 0	$ 0	$ 22
Pension Benefits
Defined benefit plan disclosure
Service cost	14	12	27	23
Interest cost	35	35	70	70
Expected return on plan assets	(45)	(39)	(91)	(78)
Amortization of actuarial loss	18	12	33	25
Other amortization, net	1	2	3	3
Net periodic cost before deferral	23	22	42	43
Other Postretirement Benefits
Defined benefit plan disclosure
Service cost	3	2	6	4
Interest cost	10	8	20	16
Expected return on plan assets	0	(1)	(1)	(2)
Amortization of actuarial loss	3	0	6	1
Other amortization, net	1	1	3	2
Net periodic cost before deferral	$ 17	$ 10	$ 34	$ 21

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The additional component of income tax expense representing amounts paid or payable which are classified as "income taxes" as determined by applying the provisions of enacted tax law to other than the taxable income (loss) from continuing operations for the period related to the enactment of the Patient Protection and Affordable Care Act (PPACA). The additional income tax expense reported for the period is attributable to the PPACA provision which changes the tax treatment of the Medicare prescription drug benefits subsidy.

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- Definition

The net amount of other amortization not presented elsewhere in the net periodic benefit cost table. Includes the amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation and the amount of the transition obligation or asset recognized in net periodic benefit cost.

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- Details

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- Definition

The amount of gains or losses recognized in net periodic benefit cost

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph h

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- Definition

An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 106
-Paragraph 518

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
-Paragraph 264

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph h

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- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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+ Details

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- Definition

The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph h

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- Definition

The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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+ Details

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