Segment Information - Reconciliation of Information Reported by Segment to Consolidated Amounts (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue:
Revenue		$ 9,483	$ 8,866	$ 8,998
Impairment		0	(81)	0
Amortization		(263)	(312)	(369)
Restructuring costs		(68)	(99)	(26)
Income/(loss) 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
Divested Businesses [Member]
Revenue:
Revenue	[1]	0	0	106
Operating Segments [Member]
Revenue:
Revenue		9,317	8,747	8,832
Income/(loss) from operations		2,378	2,116	2,181
Segment Reconciling Items [Member]
Revenue:
Revenue		166	119	60
Divested businesses	[1]	0	0	(24)
Impairment	[2]	0	(81)	0
Amortization		(263)	(312)	(369)
Restructuring costs	[3]	(68)	(99)	(26)
Transaction and transformation, net	[4]	(386)	(181)	806
Unallocated, net	[5]	(296)	(265)	(366)
Income/(loss) from operations		1,365	1,178	2,202
Interest expense		(235)	(208)	(211)
Other income, net		$ 149	$ 288	$ 701

[1] Represents the revenue and income from operations of certain Investment, Risk and Reinsurance businesses which were divested in 2021 and not classified as discontinued operations.

[2] Represents the impairment related to the net assets of our Russian business that are held outside of our Russian entities (see Note 3 — Acquisitions and Divestitures for further information).

[3] See Note 6 — Restructuring Costs for the composition of costs for 2023, 2022 and 2021.

[4] In 2023 and 2022, in addition to legal fees and other transaction costs, includes primarily consulting fees and compensation costs related to the Transformation program (see Note 6 — Restructuring Costs). For the year ended December 31, 2021, includes the $1 billion income receipt related to the termination of, and fees related to, the then-proposed Aon combination.

[5] Includes certain costs, primarily related to corporate functions which are not directly related to the segments, and certain differences between budgeted expenses determined at the beginning of the year and actual expenses that we report for U.S. GAAP purposes.