Goodwill and Other Intangibles (Narrative) (Details) - USD ($) |
3 Months Ended | 6 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Segment Reporting [Line Items] | ||||||
| Goodwill, impairment loss | $ 0 | |||||
| Indefinite-lived intangible assets | $ 0 | $ 0 | 0 | |||
| Goodwill | 24,352,000,000 | $ 23,919,000,000 | 24,352,000,000 | $ 23,919,000,000 | $ 24,337,000,000 | $ 23,306,000,000 |
| Aggregate amortization expense | 137,000,000 | $ 140,000,000 | 275,000,000 | $ 279,000,000 | ||
| Risk and Insurance Services | ||||||
| Segment Reporting [Line Items] | ||||||
| Goodwill expected to be tax deductible | 55,000,000 | 55,000,000 | ||||
| Goodwill | 19,600,000,000 | 19,600,000,000 | ||||
| Consulting | ||||||
| Segment Reporting [Line Items] | ||||||
| Goodwill expected to be tax deductible | 51,000,000 | 51,000,000 | ||||
| Goodwill | $ 4,800,000,000 | $ 4,800,000,000 | ||||
| X | ||||||||||
- Definition Amount of amortization expense for finite-lived intangible asset. Excludes goodwill and capitalized cost for software to be sold, leased, or marketed. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes. Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount of impairment loss from asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Amount of indefinite-lived intangible asset. Excludes goodwill. Reference 1: http://www.xbrl.org/2003/role/exampleRef
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|