Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Revenue	$ 9,483	$ 8,866	$ 8,998
Costs of providing services
Salaries and benefits	5,344	5,065	5,253
Other operating expenses	1,815	1,776	1,673
Depreciation	242	255	281
Amortization	263	312	369
Restructuring costs	68	99	26
Transaction and transformation	386	181	(806)
Total costs of providing services	8,118	7,688	6,796
Income from operations	1,365	1,178	2,202
Interest expense	(235)	(208)	(211)
Other income, net	149	288	701
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	1,279	1,258	2,692
Provision for income taxes	(215)	(194)	(536)
INCOME FROM CONTINUING OPERATIONS	1,064	1,064	2,156
(Loss)/income from discontinued operations, net of tax	0	(40)	2,080
NET INCOME	1,064	1,024	4,236
Income attributable to non-controlling interests	(9)	(15)	(14)
NET INCOME ATTRIBUTABLE TO WTW	$ 1,055	$ 1,009	$ 4,222
Basic earnings per share:
Income from continuing operations per share	$ 10.01	$ 9.36	$ 16.68
Income from discontinued operations per share	0	(0.36)	16.20
Basic earnings per share	10.01	9	32.88
Diluted earnings per share:
Income from continuing operations per share	9.95	9.34	16.63
(Loss)/income from discontinued operations per share	0	(0.36)	16.15
Diluted earnings per share	$ 9.95	$ 8.98	$ 32.78
NET INCOME	$ 1,064	$ 1,024	$ 4,236
Other comprehensive (loss)/income, net of tax:
Foreign currency translation	173	(499)	(87)
Defined pension and post-retirement benefits	(408)	65	260
Derivative instruments	2	(2)	2
Other comprehensive (loss)/income, net of tax, before non-controlling interests	(233)	(436)	175
Comprehensive income before non-controlling interests	831	588	4,411
Comprehensive income attributable to non-controlling interests	(11)	(14)	(16)
Comprehensive income attributable to WTW	$ 820	$ 574	$ 4,395