Condensed Consolidated Statements of Changes in Equity (Unaudited) - USD ($) $ in Millions		Total	Shares outstanding [Member]	Ordinary shares and APIC [Member]	Retained earnings [Member]	AOCL [Member]	[1]	Total WTW shareholders' equity [Member]	Non-controlling interests [Member]
Equity, beginning balance at Dec. 31, 2023		$ 9,593		$ 10,910	$ 1,466	$ (2,856)		$ 9,520	$ 73
Equity, beginning balance (in shares) at Dec. 31, 2023			102,538,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased		(101)			(101)			(101)
Shares repurchased (in shares)			(374,000)
Net income		194			190			190	4
Dividends declared		(91)			(91)			(91)
Dividends attributable to non-controlling interests		(1)							(1)
Other comprehensive (loss)/income		(49)				(49)		(49)
Issuance of shares under employee stock compensation plans (in shares)			49,000
Share-based compensation and net settlements		16		16				16
Additional non-controlling interests	[2]	3							3
Foreign currency translation		4		4				4
Equity, ending balance at Mar. 31, 2024		9,568		10,930	1,464	(2,905)		9,489	79
Equity, ending balance (in shares) at Mar. 31, 2024			102,213,000
Equity, beginning balance at Dec. 31, 2024		8,017		10,989	109	(3,158)		7,940	77
Equity, beginning balance (in shares) at Dec. 31, 2024			99,806,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased		(200)			(200)			(200)
Shares repurchased (in shares)			(607,000)
Net income		239			235			235	4
Dividends declared		(93)			(93)			(93)
Other comprehensive (loss)/income		223				223		223
Issuance of shares under employee stock compensation plans (in shares)			12,000
Share-based compensation and net settlements		33		33				33
Foreign currency translation		(5)		(5)				(5)
Equity, ending balance at Mar. 31, 2025		$ 8,214		$ 11,017	$ 51	$ (2,935)		$ 8,133	$ 81
Equity, ending balance (in shares) at Mar. 31, 2025			99,211,000

[1] Accumulated other comprehensive loss, net of tax (‘AOCL’).

[2] Attributable to the divestiture of businesses that are less than wholly-owned or the acquisition of shares previously owned by minority interest holders. In an acquisition, additional paid-in capital is adjusted as well to the extent that the consideration transferred differs from the carrying value of non-controlling interests prior to the acquisition.