Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Statement [Abstract]
Revenue	$ 2,288	$ 2,289	$ 6,772	$ 6,895
Costs of providing services
Salaries and benefits	1,413	1,396	4,186	4,135
Other operating expenses	352	419	1,053	1,315
Impairment	0	1,042	0	1,042
Depreciation	56	60	167	176
Amortization	47	56	144	176
Restructuring costs	0	8	0	29
Transaction and transformation	2	74	4	296
Total costs of providing services	1,870	3,055	5,554	7,169
Income/(loss) from operations	418	(766)	1,218	(274)
Interest expense	(65)	(65)	(194)	(197)
Other income/(loss), net	37	(1,167)	(18)	(1,118)
INCOME/(LOSS) FROM OPERATIONS BEFORE INCOME TAXES AND INTEREST IN EARNINGS OF ASSOCIATES	390	(1,998)	1,006	(1,589)
(Provision for)/benefit from income taxes	(77)	322	(121)	248
INCOME/(LOSS) FROM OPERATIONS BEFORE INTEREST IN EARNINGS OF ASSOCIATES	313	(1,676)	885	(1,341)
Interest in earnings of associates, net of tax	(7)	4	(8)	5
NET INCOME/(LOSS)	306	(1,672)	877	(1,336)
Income attributable to non-controlling interests	(2)	(3)	(7)	(8)
NET INCOME/(LOSS) ATTRIBUTABLE TO WTW	$ 304	$ (1,675)	$ 870	$ (1,344)
EARNINGS/(LOSS) PER SHARE
Basic earnings/(loss) per share	$ 3.12	$ (16.44)	$ 8.8	$ (13.11)
Diluted earnings/(loss) per share	$ 3.11	$ (16.44)	$ 8.74	$ (13.11)
Comprehensive income/(loss) before non-controlling interests	$ 303	$ (1,561)	$ 1,326	$ (1,290)
Comprehensive income attributable to non-controlling interests	(2)	(3)	(7)	(8)
Comprehensive income/(loss) attributable to WTW	$ 301	$ (1,564)	$ 1,319	$ (1,298)