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Goodwill and Other Intangibles (Narrative) (Details) - USD ($) | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023 | Dec. 31, 2022
Segment Reporting Information [Line Items] |  |  |  |  |  |
Goodwill, impairment loss | $ 0 |  |  |  |  |
Indefinite-lived intangible assets | 0 |  | $ 0 |  | $ 0 |
Goodwill | 18,235,000,000 | $ 16,655,000,000 | 18,235,000,000 | $ 16,655,000,000 | $ 17,231,000,000 | $ 16,251,000,000
Aggregate amortization expense | 90,000,000 | $ 85,000,000 | 269,000,000 | $ 257,000,000 |  |
Risk and Insurance Services |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Goodwill expected to be tax deductible | 263,000,000 |  | 263,000,000 |  |  |
Goodwill | 14,000,000,000.0 |  | 14,000,000,000.0 |  |  |
Consulting |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Goodwill expected to be tax deductible | 88,000,000 |  | 88,000,000 |  |  |
Goodwill | $ 4,200,000,000 |  | $ 4,200,000,000 |  |  |

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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 55 -Paragraph 40 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482640/350-30-55-40 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482686/350-30-45-2 + Details
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