| **Restructuring and Impairments - Restructuring Liability (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended |
|----------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Restructuring Cost and Reserve [Line Items]**                                                                      |            |   |
| Restructuring liability at beginning of year                                                                         | $ 89            | $ 39 |
| Additions                                                                                                            | 26              | 111 |
| Payments                                                                                                             | (80)            | (58) |
| Adjustments                                                                                                          | (1)             | (3) |
| Restructuring liability at end of year                                                                               | 34              | 89 |
| Employee Severance [Member]                                                                                          |            |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                      |            |   |
| Restructuring liability at beginning of year                                                                         | 72              | 31 |
| Additions                                                                                                            | 12              | 73 |
| Payments                                                                                                             | (64)            | (30) |
| Adjustments                                                                                                          | (5)             | (2) |
| Restructuring liability at end of year                                                                               | 15              | 72 |
| Employee Relocation [Member]                                                                                         |            |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                      |            |   |
| Restructuring liability at beginning of year                                                                         | 0               | 0 |
| Additions                                                                                                            | 3               | 8 |
| Payments                                                                                                             | (3)             | (8) |
| Adjustments                                                                                                          | 0               | 0 |
| Restructuring liability at end of year                                                                               | 0               | 0 |
| Lease Vacancy [Member] [Domain]                                                                                      |            |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                      |            |   |
| Restructuring liability at beginning of year                                                                         | 17              | 0 |
| Additions                                                                                                            | 6               | 19 |
| Payments                                                                                                             | (9)             | (4) |
| Adjustments                                                                                                          | 4               | 2 |
| Restructuring liability at end of year                                                                               | 18              | 17 |
| Other Restructuring [Member]                                                                                         |            |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                      |            |   |
| Restructuring liability at beginning of year                                                                         | 0               | 8 |
| Additions                                                                                                            | 5               | 11 |
| Payments                                                                                                             | (4)             | (16) |
| Adjustments                                                                                                          | 0               | (3) |
| Restructuring liability at end of year                                                                               | $ 1             | $ 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
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585
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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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| X                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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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
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section P -Subsection 3, 4
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of any reversal and other adjustment made during the period to the amount of a previously accrued liability for a specified type of restructuring cost, excluding adjustments for costs incurred during the period, costs settled during the period, and foreign currency translation adjustments.
+ References
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