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Restructuring Costs (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2021
Restructuring Cost and Reserve [Line Items] |  |  |
Estimated remaining costs | $ 219 | $ 219 |
JLT Transaction |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred in other restructuring |  | 427 | $ 163
Acquisition Related | JLT Transaction |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred in other restructuring |  | 427 | 163
Acquisition Related | JLT Transaction | Corporate |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred in other restructuring |  | 96 | 31
RIS |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Exit costs | $ 89 |  |
RIS | Acquisition Related | JLT Transaction |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred in other restructuring |  | 254 | 84
Consulting | Acquisition Related | JLT Transaction |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |
Costs incurred in other restructuring |  | $ 77 | $ 48

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