Consolidated Statements of Changes in Equity - USD ($) $ 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, 2020		$ 10,932		$ 10,748	$ 2,434	$ (3)	$ (2,359)		$ 10,820	$ 112
Equity, beginning balance (in shares) at Dec. 31, 2020			128,965,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased		(1,627)			(1,627)				(1,627)
Shares repurchased (in shares)			(7,155,000)
Net income		4,236			4,222				4,222	14
Dividends declared		(384)			(384)				(384)
Dividends attributable to non-controlling interests		(29)								(29)
Other comprehensive (loss)/income		175					173		173	2
Issuance of shares under employee stock compensation plans		10		10					10
Issuance of shares under employee stock compensation plans (in shares)			246,000
Share-based compensation and net settlements		47		47					47
Reduction of non-controlling interests	[2]	(59)		(8)					(8)	(51)
Foreign currency translation		7		7					7
Equity, ending balance at Dec. 31, 2021		13,308		10,804	4,645	(3)	(2,186)		13,260	48
Equity, ending balance (in shares) at Dec. 31, 2021			122,056,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased		(3,530)			(3,530)				(3,530)
Shares repurchased (in shares)			(15,729,000)
Net income		1,024			1,009				1,009	15
Dividends declared		(360)			(360)				(360)
Dividends attributable to non-controlling interests		(10)								(10)
Other comprehensive (loss)/income		(436)					(435)		(435)	(1)
Issuance of shares under employee stock compensation plans		7		7					7
Issuance of shares under employee stock compensation plans (in shares)			429,000
Share-based compensation and net settlements		54		54					54
Additional non-controlling interests		27								27
Reduction of non-controlling interests	[2]			2					2	(2)
Foreign currency translation		9		9					9
Equity, ending balance at Dec. 31, 2022		10,093		10,876	1,764	(3)	(2,621)		10,016	77
Equity, ending balance (in shares) at Dec. 31, 2022			106,756,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased		(1,000)		(3)	(1,000)	3			(1,000)
Shares repurchased (in shares)			(4,483,000)
Net income		1,064			1,055				1,055	9
Dividends declared		(353)			(353)				(353)
Dividends attributable to non-controlling interests		(13)								(13)
Other comprehensive (loss)/income		(233)					(235)		(235)	2
Issuance of shares under employee stock compensation plans		$ 0		0					0
Issuance of shares under employee stock compensation plans (in shares)		265,000	265,000
Share-based compensation and net settlements		$ 89		89					89
Reduction of non-controlling interests	[2]	(49)		(47)					(47)	(2)
Foreign currency translation		(5)		(5)					(5)
Equity, ending balance at Dec. 31, 2023		$ 9,593		$ 10,910	$ 1,466	$ 0	$ (2,856)		$ 9,520	$ 73
Equity, ending balance (in shares) at Dec. 31, 2023			102,538,000

[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.