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Accelerating Aon United Program - Changes in the Company’s Liabilities for the Program (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2024 | Mar. 31, 2023
Restructuring Reserve [Roll Forward] |  |
Charges | $ 119 | $ 0
Accelerating Aon United Program |  |
Restructuring Reserve [Roll Forward] |  |
Liability Balance as of January 1, 2024 | 100 |
Charges | 119 |
Cash payments | (37) |
Foreign currency translation and other | (1) |
Non-cash charges | (48) |
Liability balance as of March 31, 2024 | 133 |
Liability balance as of March 31, 2024 | 254 |
Accelerating Aon United Program | Technology and other |  |
Restructuring Reserve [Roll Forward] |  |
Liability Balance as of January 1, 2024 | 14 |
Charges | 19 |
Cash payments | (12) |
Foreign currency translation and other | 0 |
Non-cash charges | (7) |
Liability balance as of March 31, 2024 | 14 |
Liability balance as of March 31, 2024 | 33 |
Accelerating Aon United Program | Workforce optimization |  |
Restructuring Reserve [Roll Forward] |  |
Liability Balance as of January 1, 2024 | 86 |
Charges | 64 |
Cash payments | (25) |
Foreign currency translation and other | (1) |
Non-cash charges | (5) |
Liability balance as of March 31, 2024 | 119 |
Liability balance as of March 31, 2024 | 167 |
Accelerating Aon United Program | Asset impairments |  |
Restructuring Reserve [Roll Forward] |  |
Liability Balance as of January 1, 2024 | 0 |
Charges | 36 |
Cash payments | 0 |
Foreign currency translation and other | 0 |
Non-cash charges | (36) |
Liability balance as of March 31, 2024 | 0 |
Liability balance as of March 31, 2024 | $ 54 |

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