XML 22 R8.htm IDEA: XBRL DOCUMENT
v3.20.4

Consolidated Statements Of Equity (Parenthetical) - $ / shares | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Statement of Stockholders' Equity [Abstract] |  |  |
Dividends equivalents declared per share (in dollars per share) | $ 1.84 | $ 1.74 | $ 1.58
Dividends declared per share (in dollars per share) | $ 1.84 | $ 1.74 | $ 1.58

X
- Definition Common Stock, Dividends Per Share, Cash, Declared + References No definition available. + Details
Name: | mmc_CommonStockDividendsPerShareCashDeclared
Namespace Prefix: | mmc_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Dividend Equivalents Per Share, Cash, Declared + References No definition available. + Details
Name: | mmc_DividendEquivalentsPerShareCashDeclared
Namespace Prefix: | mmc_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_StatementOfStockholdersEquityAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration