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Restructuring - Schedule of Restructuring and Related Expense (Details) $ in Millions | 12 Months Ended | 24 Months Ended
--- | --- | ---
Dec. 31, 2018 USD ($) | Dec. 31, 2018 USD ($)
Restructuring Cost and Reserve [Line Items] |  |
Estimated Remaining Costs | $ 243 | $ 243
2017 Plan |  |
Restructuring Cost and Reserve [Line Items] |  |
Incurred restructuring cost | 485 | 982
Expected cost | 1,225 | 1,225
Workforce reduction | 2017 Plan |  |
Restructuring Cost and Reserve [Line Items] |  |
Incurred restructuring cost | 115 | 414
Estimated Remaining Costs | 36 | 36
Expected cost | 450 | 450
Technology rationalization | 2017 Plan |  |
Restructuring Cost and Reserve [Line Items] |  |
Incurred restructuring cost | 47 | 80
Estimated Remaining Costs | 50 | 50
Expected cost | 130 | 130
Incurred contract termination costs | 5 | 6
Expected contract termination cost remaining | 15 | 15
Lease consolidation | 2017 Plan |  |
Restructuring Cost and Reserve [Line Items] |  |
Incurred restructuring cost | 28 | 36
Estimated Remaining Costs | 29 | 29
Expected cost | 65 | 65
Incurred contract termination costs | 25 | 33
Expected contract termination cost remaining | 80 | 80
Asset impairments | 2017 Plan |  |
Restructuring Cost and Reserve [Line Items] |  |
Incurred restructuring cost | 13 | 39
Estimated Remaining Costs | 11 | 11
Expected cost | 50 | 50
Other Restructuring | 2017 Plan |  |
Restructuring Cost and Reserve [Line Items] |  |
Incurred restructuring cost | 282 | 413
Estimated Remaining Costs | 117 | 117
Expected cost | 530 | 530
Incurred contract termination costs | 85 | 88
Expected contract termination cost remaining | $ 95 | $ 95

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