Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Revenue	$ 8,866	$ 8,998	$ 8,615
Costs of providing services
Salaries and benefits	5,065	5,253	5,157
Other operating expenses	1,776	1,673	1,697
Depreciation	255	281	307
Amortization	312	369	461
Restructuring costs	99	26	24
Transaction and transformation, net	181	(806)	110
Total costs of providing services	7,688	6,796	7,756
Income from operations	1,178	2,202	859
Interest expense	(208)	(211)	(244)
Other income, net	288	701	396
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	1,258	2,692	1,011
Provision for income taxes	(194)	(536)	(249)
INCOME FROM CONTINUING OPERATIONS	1,064	2,156	762
(Loss)/income from discontinued operations, net of tax	(40)	2,080	258
NET INCOME	1,024	4,236	1,020
Income attributable to non-controlling interests	(15)	(14)	(24)
NET INCOME ATTRIBUTABLE TO WTW	$ 1,009	$ 4,222	$ 996
Basic earnings per share:
Income from continuing operations per share	$ 9.36	$ 16.68	$ 5.69
Income from discontinued operations per share	(0.36)	16.20	1.99
Basic earnings per share	9.00	32.88	7.68
Diluted earnings per share:
Income from continuing operations per share	9.34	16.63	5.67
(Loss)/income from discontinued operations per share	(0.36)	16.15	1.98
Diluted earnings per share	$ 8.98	$ 32.78	$ 7.65
NET INCOME	$ 1,024	$ 4,236	$ 1,020
Other comprehensive (loss)/income, net of tax:
Foreign currency translation	(499)	(87)	139
Defined pension and post-retirement benefits	65	260	(266)
Derivative instruments	(2)	2	(4)
Other comprehensive (loss)/income, net of tax, before non-controlling interests	(436)	175	(131)
Comprehensive income before non-controlling interests	588	4,411	889
Comprehensive income attributable to non-controlling interests	(14)	(16)	(25)
Comprehensive income attributable to WTW	$ 574	$ 4,395	$ 864