| **Postretirement Benefits - Components of Postretirement Benefits Expense (Income) (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended | 9 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                                                |           |           |   |   |
| Increase (Decrease) In Pension and Other Postretirement Benefit Expense                                                                       |           |           | $ 1 |   |
| Pension Plan, Defined Benefit [Member]                                                                                                        |           |           |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                                                |           |           |   |   |
| Service cost for benefits earned during the period                                                                                            | 3              | 5              | 9 | 15 |
| Interest on obligation                                                                                                                        | 39             | 36             | 118 | 108 |
| Amortization of cumulative loss                                                                                                               | 23             | 31             | 70 | 95 |
| Amortization of prior service benefit                                                                                                         | 0              | 1              | 0 | 1 |
| Contractual termination benefits                                                                                                              | 14             | 0              | 14 | 0 |
| Premiums on pension insurance                                                                                                                 | 0              | 0              | 0 | 1 |
| Expected return on assets                                                                                                                     | (48)           | (48)           | (144) | (142) |
| Net postretirement benefits expense                                                                                                           | 31             | 25             | 67 | 78 |
| Other Postretirement Benefit Plan, Defined Benefit [Member]                                                                                   |           |           |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                                                |           |           |   |   |
| Service cost for benefits earned during the period                                                                                            | 2              | 1              | 4 | 5 |
| Interest on obligation                                                                                                                        | 17             | 16             | 51 | 47 |
| Amortization of cumulative loss                                                                                                               | 4              | 7              | 12 | 22 |
| Amortization of prior service benefit                                                                                                         | (1)            | (1)            | (3) | (3) |
| Contractual termination benefits                                                                                                              | 0              | 0              | 0 | 0 |
| Premiums on pension insurance                                                                                                                 | 0              | 0              | 0 | 0 |
| Expected return on assets                                                                                                                     | (8)            | (8)            | (24) | (25) |
| Net postretirement benefits expense                                                                                                           | 14             | 15             | 40 | 46 |
| Facility Closing [Member] | Chatham [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]                                    |           |           |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                                                |           |           |   |   |
| Defined Benefit Plan, Cost of Providing Special or Contractual Termination Benefits Recognized During Period                                  | 14             |           |   |   |
| Effect Of Remeasurement On Plan [Member]                                                                                                      |           |           |   |   |
| **Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]**                                                |           |           |   |   |
| Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Tax                                     |           |           | $ 10 |   |

| X                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Increase (Decrease) In Pension and Other Postretirement Benefit Expense
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of gains or losses recognized in net periodic benefit cost.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
If applicable, the cost of providing special or contractual termination benefits recognized during the period on the projected benefit obligation.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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 (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.
+ References
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| X                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of other defined benefit plan costs.
+ References
No definition available.
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| X                                                                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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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.
+ References
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| 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
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| X                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Period expense related to postemployment benefits.
+ References
No definition available.
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