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Restructuring - Narrative (Details) - 2017 Plan $ in Millions | 3 Months Ended | 6 Months Ended | 18 Months Ended
--- | --- | --- | ---
Jun. 30, 2018 USD ($) | Jun. 30, 2018 USD ($) job_elimination | Jun. 30, 2018 USD ($) job_elimination
Restructuring Cost and Reserve [Line Items] |  |  |
Expected total cost | $ 1,025 | $ 1,025 | $ 1,025
Number of positions eliminated to date | job_elimination |  |  | 3,337
Costs incurred | 195 | 269 | $ 766
Workforce reduction |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Expected total cost | 420 | 420 | 420
Costs incurred | 33 | 66 | 365
Technology rationalization |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Expected total cost | 130 | 130 | 130
Costs incurred | 8 | 18 | 51
Lease consolidation |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Expected total cost | 60 | 60 | 60
Costs incurred | 10 | 13 | 21
Asset impairments |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Expected total cost | 40 | 40 | 40
Costs incurred | 8 | 9 | 35
Other Restructuring |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Expected total cost | 375 | 375 | 375
Costs incurred | $ 136 | $ 163 | $ 294
Minimum |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Expected number of positions eliminated | job_elimination |  | 4,200 |
Maximum |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Expected number of positions eliminated | job_elimination |  | 4,800 |

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