v3.25.4

Revenue (Narrative) (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2025 USD ($) installment | Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($)
Disaggregation of Revenue [Line Items] |  |  |
Percentage of total revenue | 1.00% |  |
Number of installments for brokerage revenue | installment | 4 |  |
Contract with customer, performance obligation satisfied in previous period | $ 83 | $ 73 | $ 71
Capitalized contract cost, amortization | 2,100 | 1,900 | $ 1,800
Deferred Implementation Costs |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Capitalized contract cost, net | 1 | 3 |
Costs to Obtain |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Capitalized contract cost, net | 459 | 396 |
Costs to Fulfill |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Capitalized contract cost, net | $ 438 | $ 397 |
Mercer Consulting Group |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Consulting revenue, payment terms (in days) | 30 days |  |
Risk and Insurance Services |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Insurance brokerage commissions, payment terms (in days) | 30 days |  |
Consulting | Mercer Consulting Group |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue from contract with customer, percent | 51.00% |  |
Minimum |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Capitalized contract cost, amortization period | 3 months |  |
Minimum | Risk and Insurance Services |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Estimated brokerage revenue, payment terms (in months) | 12 months |  |
Reinsurance brokerage revenue, payment terms (in months) | 12 months |  |
Minimum | Consulting | Marsh Management Consulting |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Consulting revenue, payment terms (in days) | 30 days |  |
Maximum |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Capitalized contract cost, amortization period | 6 months |  |
Maximum | Risk and Insurance Services |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Estimated brokerage revenue, payment terms (in months) | 18 months |  |
Reinsurance brokerage revenue, payment terms (in months) | 18 months |  |
Maximum | Consulting | Marsh Management Consulting |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Consulting revenue, payment terms (in days) | 60 days |  |

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