Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net income	$ 2,720	$ 2,628	$ 2,646
Adjustments to reconcile net income to cash provided by operating activities:
Gain from sales of businesses	(337)	(4)	(54)
Depreciation of fixed assets	183	167	151
Amortization and impairment of intangible assets	503	89	113
Share-based compensation expense	474	438	397
Deferred income taxes	(311)	(373)	(252)
Other, net	(134)	28	170
Change in assets and liabilities:
Receivables, net	(312)	(188)	(96)
Accounts payable and accrued liabilities	393	13	(22)
Accelerating Aon United Program liabilities	17	99	0
Current income taxes	0	174	216
Pension, other postretirement and postemployment liabilities	(18)	8	(53)
Other assets and liabilities	(143)	356	3
Cash provided by operating activities	3,035	3,435	3,219
Cash flows from investing activities
Proceeds from investments	212	76	110
Purchases of investments	(172)	(67)	(107)
Net sales of short-term investments - non fiduciary	151	85	(175)
Acquisition of businesses, net of cash and funds held on behalf of clients	(3,506)	(35)	(162)
Sale of businesses, net of cash and funds held on behalf of clients	700	5	81
Capital expenditures	(218)	(252)	(196)
Cash used for investing activities	(2,833)	(188)	(449)
Cash flows from financing activities
Share repurchase	(1,000)	(2,700)	(3,203)
Proceeds from issuance of shares	79	72	58
Cash paid for employee taxes on withholding shares	(202)	(241)	(215)
Commercial paper issuances, net of repayments	(591)	(27)	(65)
Issuance of debt	7,926	744	1,967
Repayment of debt	(4,928)	(350)	(500)
Increase in fiduciary liabilities, net of fiduciary receivables	280	358	702
Cash dividends to shareholders	(562)	(489)	(463)
Redeemable and non-redeemable noncontrolling interests, and other financing activities	(206)	(232)	(71)
Cash provided by (used for) financing activities	796	(2,865)	(1,790)
Effect of exchange rates on cash and cash equivalents and funds held on behalf of clients	(387)	264	(549)
Net increase in cash and cash equivalents and funds held on behalf of clients	611	646	431
Cash, cash equivalents and funds held on behalf of clients at beginning of year	7,722	7,076	6,645
Cash, cash equivalents and funds held on behalf of clients at end of year	8,333	7,722	7,076
Reconciliation of cash and cash equivalents and funds held on behalf of clients:
Cash and cash equivalents	1,085	778	690
Cash and cash equivalents and funds held on behalf of clients classified as held for sale	1	43	0
Funds held on behalf of clients	7,247	6,901	6,386
Total cash and cash equivalents and funds held on behalf of clients	8,333	7,722	7,076
Supplemental disclosures:
Interest paid	658	446	351
Income taxes paid, net of refunds	$ 1,053	$ 740	$ 546