Condensed Consolidated Statements of Changes in Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions		Total	Shares outstanding [Member]	Ordinary shares and APIC [Member]	Retained earnings [Member]	Treasury Stock Common [Member]	AOCL [Member]	[1]	Total WTW shareholders' equity [Member]	Non-controlling interests [Member]
Equity, beginning balance at Dec. 31, 2022		$ 10,093		$ 10,876	$ 1,764	$ (3)	$ (2,621)		$ 10,016	$ 77
Equity, beginning balance (in shares) at Dec. 31, 2022			106,756
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased (in shares)			(432)
Shares repurchased		(104)		(3)	(104)	3			(104)
Net income		206			203				203	3
Dividends declared		(89)			(89)				(89)
Other comprehensive (loss)/income		53					53		53
Issuance of shares under employee stock compensation plans (in shares)			59
Share-based compensation and net settlements		18		18					18
Foreign currency translation		(1)		(1)					(1)
Equity, ending balance at Mar. 31, 2023		10,176		10,890	1,774	0	(2,568)		10,096	80
Equity, ending balance (in shares) at Mar. 31, 2023			106,383
Equity, beginning balance at Dec. 31, 2023		9,593		10,910	1,466	0	(2,856)		9,520	73
Equity, beginning balance (in shares) at Dec. 31, 2023			102,538
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased (in shares)			(374)
Shares repurchased		(101)			(101)				(101)
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		0		0					0
Issuance of shares under employee stock compensation plans (in shares)			49
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	$ 0	$ (2,905)		$ 9,489	$ 79
Equity, ending balance (in shares) at Mar. 31, 2024			102,213

[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.