| **Restructuring and Impairments - Restructuring Reserve by Type (Details) - USD ($) $ in Millions** | 3 Months Ended | 6 Months Ended |        |        |
|-----------------------------------------------------------------------------------------------------|----------------|----------------|--------|--------|
||
| **Restructuring Cost and Reserve [Line Items]**                                                     |           |           |   |   |   |   |
| Restructuring charges                                                                               | $ 3            | $ 6            | $ 6    | $ 9    |   |   |
| Restructuring Reserve                                                                               | 22             | 18             | 22     | 18     | $ 68 | $ 20 |
| Restructuring and Related Cost, Incurred Cost                                                       |           |           | 6      | 7      |   |   |
| Payments for Restructuring                                                                          |           |           | 52     | 8      |   |   |
| Restructuring Reserve, Accrual Adjustment                                                           |           |           | 0      | (1)    |   |   |
| Employee Severance [Member]                                                                         |           |           |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                     |           |           |   |   |   |   |
| Restructuring Reserve                                                                               | 19             | 10             | 19     | 10     | 62 | 8 |
| Restructuring and Related Cost, Incurred Cost                                                       |           |           | 6      | 7      |   |   |
| Payments for Restructuring                                                                          |           |           | 49     | 4      |   |   |
| Restructuring Reserve, Accrual Adjustment                                                           |           |           | 0      | (1)    |   |   |
| Lease Vacancy [Member] [Domain]                                                                     |           |           |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                     |           |           |   |   |   |   |
| Restructuring Reserve                                                                               | 2              | 7              | 2      | 7      | 5 | 11 |
| Restructuring and Related Cost, Incurred Cost                                                       |           |           | 0      | 0      |   |   |
| Payments for Restructuring                                                                          |           |           | 3      | 4      |   |   |
| Restructuring Reserve, Accrual Adjustment                                                           |           |           | 0      | 0      |   |   |
| Other Restructuring [Member]                                                                        |           |           |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                     |           |           |   |   |   |   |
| Restructuring Reserve                                                                               | $ 1            | $ 1            | 1      | 1      | $ 1 | $ 1 |
| Restructuring and Related Cost, Incurred Cost                                                       |           |           | 0      | 0      |   |   |
| Payments for Restructuring                                                                          |           |           | 0      | 0      |   |   |
| Restructuring Reserve, Accrual Adjustment                                                           |           |           | $ 0    | $ 0    |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense (reversal of expense) which increases (decreases) the restructuring reserve from an adjustment to a previously accrued restructuring liability.
+ References
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| X                                                                                                                                                               |
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| X                                                                                                                                                            |
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| X                                                                                                                                                                |
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