XML 42 R30.htm IDEA: XBRL DOCUMENT
v3.23.3

Fiduciary Assets and Liabilities (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2023
Fiduciary Assets And Liabilities [Abstract] |
Schedule of Reclassification of Fiduciary Assets and Liabilities | The presentation in the December 31, 2022 consolidated balance sheet was conformed to the current presentation as follows:
(In millions) | As Reported | As Reclassified
Total current assets | $ | 8,299 |  | $ | 18,959 |
Total assets | $ | 33,454 |  | $ | 44,114 |
Total current liabilities | $ | 7,172 |  | $ | 17,832 |

X
- Definition Fiduciary Assets And Liabilities [Abstract] + References No definition available. + Details
Name: | mmc_FiduciaryAssetsAndLiabilitiesAbstract
Namespace Prefix: | mmc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reclassification Of Fiduciary Assets And Liabilities + References No definition available. + Details
Name: | mmc_ReclassificationOfFiduciaryAssetsAndLiabilitiesTableTextBlock
Namespace Prefix: | mmc_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration