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 shares [Member]	AOCL [Member]	[1]	Total WTW shareholders' equity [Member]	Non-controlling interests [Member]
Equity, beginning balance at Dec. 31, 2021	$ 13,308		$ 10,804	$ 4,645	$ (3)	$ (2,186)		$ 13,260	$ 48
Equity, beginning balance (in shares) at Dec. 31, 2021		122,056
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	125			122				122	3
Shares repurchased (in shares)		(9,860)
Shares repurchased	(2,250)			(2,250)				(2,250)
Dividends declared	(94)			(94)				(94)
Dividends attributable to non-controlling interests	(1)								(1)
Other comprehensive income (loss)	(56)					(56)		(56)
Issuance of shares under employee stock compensation plans	1		1					1
Issuance of shares under employee stock compensation plans (in shares)		17
Share-based compensation and net settlements	20		20					20
Additional non-controlling interests	21								21
Foreign currency translation	1		1					1
Equity, ending balance at Mar. 31, 2022	11,075		10,826	2,423	(3)	(2,242)		11,004	71
Equity, ending balance (in shares) at Mar. 31, 2022		112,213
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]
Net income	206			203				203	3
Shares repurchased (in shares)		(432)	3		(3)
Shares repurchased	(104)			(104)				(104)
Dividends declared	(89)			(89)				(89)
Other comprehensive income (loss)	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

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