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Restructuring - Schedule of Restructuring and Related Expenses (Details) - 2017 Plan $ in Millions | 3 Months Ended | 9 Months Ended | 21 Months Ended
--- | --- | --- | ---
Sep. 30, 2018 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2018 USD ($)
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred | $ 97 | $ 366 | $ 863
Estimated Remaining Costs | 162 | 162 | 162
Expected total cost | 1,025 | 1,025 | 1,025
Workforce reduction |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred | 18 | 84 | 383
Estimated Remaining Costs | 37 | 37 | 37
Expected total cost | 420 | 420 | 420
Technology rationalization |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred | 12 | 30 | 63
Estimated Remaining Costs | 67 | 67 | 67
Expected total cost | 130 | 130 | 130
Contract termination costs incurred | 1 | 2 | 3
Expected contract termination cost remaining | 15 | 15 | 15
Lease consolidation |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred | 11 | 24 | 32
Estimated Remaining Costs | 28 | 28 | 28
Expected total cost | 60 | 60 | 60
Contract termination costs incurred | 11 | 23 | 31
Expected contract termination cost remaining | 80 | 80 | 80
Asset impairments |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred | 2 | 11 | 37
Estimated Remaining Costs | 3 | 3 | 3
Expected total cost | 40 | 40 | 40
Other costs associated with restructuring and separation |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred | 54 | 217 | 348
Estimated Remaining Costs | 27 | 27 | 27
Expected total cost | 375 | 375 | 375
Contract termination costs incurred | 3 | 82 | 85
Expected contract termination cost remaining | $ 85 | $ 85 | $ 85

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