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Restructuring Costs (Restructuring and Related Costs Incurred) (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022
Restructuring Cost and Reserve [Line Items] |  |  |  |
Total | $ 65 | $ 28 | $ 118 | $ 58
Corporate |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Total | 27 | 13 | 39 | 21
Risk and Insurance Services |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Total | 31 | 11 | 63 | 26
Consulting |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Total | $ 7 | $ 4 | $ 16 | $ 11

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