| **Postretirement Benefits - Narrative (Details) (USD $)Share data in Millions, unless otherwise specified** | 3 Months Ended | 12 Months Ended |               | 12 Months Ended | 3 Months Ended | 18 Months Ended | 3 Months Ended |                 |                 |                 |           | 12 Months Ended |               |               |        |           |            |            |            |        |
|-------------------------------------------------------------------------------------------------------------|----------------|-----------------|---------------|-----------------|----------------|-----------------|----------------|-----------------|-----------------|-----------------|-----------|-----------------|---------------|---------------|--------|-----------|------------|------------|------------|--------|
||
| **Compensation and Retirement Disclosure [Abstract]**                                                       |           |            |          |            |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Defined Benefit Plan, Fair Value of Plan Assets                                                             |           |            |          |            |           |            |           | $ 2,519,000,000 | $ 2,411,000,000 | $ 2,392,000,000 |      | $ 447,000,000   | $ 437,000,000 | $ 463,000,000 |   |      |       |       |       |   |   |   |   |   |   | $ 8,000,000 | $ 8,000,000 | $ 1,000,000 | $ 1,000,000 |   |   |   |   |   | $ 207,000,000 | $ 463,000,000 | $ 28,000,000 | $ 82,000,000 | $ 0 | $ 0 | $ 0 | $ 0 |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**              |           |            |          |            |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Defined Benefit Plan, Target Plan Asset Allocations                                                         |           |            |          |            |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   | 55.00% | 30.00% | 10.00% | 5.00% | 15.00% |   |   |   |   |   |   |   |   |
| Pension and other postretirment charges due to reduction in workfroce                                       |           |            |          | 7,000,000       |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Accumulated benefit obligation for pension benefits                                                         | 3,900,000,000  |            | 3,900,000,000 | 4,400,000,000   |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Deferred taxes related to the Company's postretirement benfit plans                                         |           |            |          |            |           | 539,000,000     |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Amounts contributed to meet regulatory funding requirements                                                 |           |            |          |            |           |            |           | 165,000,000     | 157,000,000     |            |      | 3,000,000       | 19,000,000    |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Amounts expected to be contributed to pension plans in 2014                                                 |           |            |          |            |           |            | 180,000,000    |            |            |            | 2,000,000 |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Benefits paid                                                                                               |           |            |          |            |           |            |           | 333,000,000     | 328,000,000     |            |      | 188,000,000     | 187,000,000   |          |   |      |       | 14,000,000 | 13,000,000 |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Benefits paid from Company assets                                                                           |           |            |          |            |           |            |           |            |            |            |      | 60,000,000      | 75,000,000    |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Curtailments                                                                                                | 4,000,000      |            |          |            |           |            |           | 33,000,000      | (4,000,000)     |            |      | 0               | 0             |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Defined Benefit Plan, Benefit Obligation, Period Increase (Decrease)                                        | 33,000,000     |            |          |            |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Pension curtailment gain                                                                                    |           |            |          |            |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   | 8,000,000 |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Contractual termination benefits                                                                            |           |            |          |            |           |            |           | 0               | 2,000,000       | 38,000,000      |      | 0               | (2,000,000)   | 6,000,000     |   |      |       |       |       |   | 35,000,000 |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Other post-employment benefit charges                                                                       |           |            |          |            |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   | 13,000,000 | 5,000,000 | 2,000,000 |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Increase in postretirement benefit expense                                                                  |           | 15,000,000      | (58,000,000)  | (79,000,000)    | 9,000,000      |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Prior service cost (benefit)                                                                                |           |            |          |            | (302,000,000)  |            |           | (1,000,000)     | (1,000,000)     | 0               |      | 0               | 0             | 302,000,000   |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Amounts recognized in our accumulated other comprehensive loss consist of:                                  |           |            |          |            |           |            |           | (585,000,000)   | 357,000,000     | 267,000,000     |      | (200,000,000)   | (88,000,000)  | 893,000,000   |   |      |       |       |       |   |   |   |   |   | 200,000,000 |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Effect of re-measurement increased postretirement benefits expense                                          |           | 9,000,000       |          |            |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Plan participants' contributions                                                                            |           |            |          |            |           |            |           | 0               | 0               |            |      | 28,000,000      | 20,000,000    |          | 0      | 3,000,000 | 10,000,000 |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Number of employees and beneficiaries included in Company's retiree population                              |           |            |          | 38,000          |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Defined benefit plan, weighted average rate of increase in in per capita cost percent of benefit obligation |           |            |          | 9.20%           |           |            |           |            |            |            |      |            | 90.00%        |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Postretirement benefit obligation projection for 2014                                                       |           |            |          |            |           |            |           |            |            |            |      |            | 8.25%         |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Defined Benefit Plan, Ultimate Health Care Cost Trend Rate                                                  |           |            |          |            |           |            |           |            |            |            |      |            | 5.00%         |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Defined Contribution Plan, Cost Recognized                                                                  |           |            | $ 27,000,000  | $ 41,000,000    | $ 33,000,000   |            |           |            |            |            |      |            |          |          |   |      |       |       |       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Contribution to the Supplemental Trust shares                                                               |           |            |          |            |           |            |           |            |            |            |      |            |          |          |   |      |       |       |       | 25.5   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |

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Contribution To The Trust Shares
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| - Definition
Defined benefit plan, benefits paid from Company assets
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Defined benefit plan, weighted average rate of increase in in per capita cost percent of benefit obligation
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| X                                                                                                                                                                                                                                                                                                                         |
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| - Definition
Increase (Decrease) In Pension and Other Postretirement Benefit Expense
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| - Definition
Number Of Former Employees And Their Beneficiaries Included In Retiree Population
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| - Definition
Pension and other postretirment charges due to reduction in workfroce
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| - Definition
Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and other assets expected to be realized or consumed after one year or normal operating cycle, if longer.
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| - Definition
For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.
+ References
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| - Definition
Net increase or decrease in the plan benefit obligation during the reporting period.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.
+ References
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| - Definition
The increase in the fair value of plan assets from contributions made by the employer.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of contributions made by plan participants. This item represents a periodic increase to the plan obligation and an increase to plan assets.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
If applicable, the cost of providing special or contractual termination benefits recognized during the period on the projected benefit obligation.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of decrease that is related to an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of net gain (loss) recognized in net periodic benefit cost as a result of an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.
+ References
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| - Definition
Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Target allocation of investments of this type to total plan assets presented on a weighted average basis.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c)(i) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e2446-114920
+ Details**Name:**us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The ultimate trend rate for health care costs.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920
+ Details**Name:**us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of the cost recognized during the period for defined contribution plans.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The increase (decrease) during the reporting period in the amount due to fund non-pension benefits provided to former, retired, and disabled employees.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax of cost (credit) of benefit changes attributable to plan participants' prior service resulting from a plan amendment or plan initiation that has not been recognized in net periodic benefit cost (credit).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (j) -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669646-108580
+ Details**Name:**us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax, after reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i-k) -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669646-108580
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| X                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Period expense related to postemployment benefits.
+ References
No definition available.
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