Goodwill and Other Intangibles (Changes in the Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Goodwill [Roll Forward]
Balance at January 1,	$ 23,306	$ 17,231
Goodwill acquired	100	430
Other adjustments	513	(145)
Balance at June 30,	$ 23,919	$ 17,516

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.

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+ Details

MARSH & MCLENNAN COMPANIES, INC. 10-Q