Goodwill and Other Intangible Assets - Components of Goodwill (Details) $ in Millions	9 Months Ended
	Sep. 30, 2025 USD ($)
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	$ 10,072
Accumulated impairment losses, beginning balance	(1,273)
Goodwill, net, beginning balance	8,799
Goodwill acquired	9
Foreign exchange	128
Goodwill, gross, ending balance	10,209
Accumulated impairment losses, ending balance	(1,273)
Goodwill, net, ending balance	8,936
HWC [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	7,276
Accumulated impairment losses, beginning balance	(911)
Goodwill, net, beginning balance	6,365
Goodwill acquired	0
Foreign exchange	41
Goodwill, gross, ending balance	7,317
Accumulated impairment losses, ending balance	(911)
Goodwill, net, ending balance	6,406
R&B [Member]
Goodwill [Roll Forward]
Goodwill, gross, beginning balance	2,796
Accumulated impairment losses, beginning balance	(362)
Goodwill, net, beginning balance	2,434
Goodwill acquired	9
Foreign exchange	87
Goodwill, gross, ending balance	2,892
Accumulated impairment losses, ending balance	(362)
Goodwill, net, ending balance	$ 2,530

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

WILLIS TOWERS WATSON PLC 10-Q