Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net income	$ 2,628	$ 2,646	$ 1,308
Adjustments to reconcile net income to cash provided by operating activities:
Gain from sales of businesses	(4)	(54)	(142)
Depreciation of fixed assets	167	151	179
Amortization and impairment of intangible assets	89	113	147
Share-based compensation expense	438	397	449
Deferred income taxes	(373)	(252)	11
Other, net	28	170	5
Change in assets and liabilities:
Receivables, net	(188)	(96)	(119)
Accounts payable and accrued liabilities	13	(22)	264
Accelerating Aon United Program liabilities	99	0	0
Current income taxes	174	216	200
Pension, other postretirement and postemployment liabilities	8	(53)	(124)
Other assets and liabilities	356	3	4
Cash provided by operating activities	3,435	3,219	2,182
Cash flows from investing activities
Proceeds from investments	76	110	58
Purchases for investments	(67)	(107)	(91)
Net sales (purchases) of short-term investments - non fiduciary	85	(175)	15
Acquisition of businesses, net of cash and funds held on behalf of clients	(35)	(162)	(14)
Sale of businesses, net of cash and funds held on behalf of clients	5	81	218
Capital expenditures	(252)	(196)	(137)
Cash provided by (used for) investing activities	(188)	(449)	49
Cash flows from financing activities
Share repurchase	(2,700)	(3,203)	(3,543)
Proceeds from issuance of shares	72	58	55
Cash paid for employee taxes on withholding shares	(241)	(215)	(185)
Commercial paper issuances, net of repayments	(27)	(65)	671
Issuance of debt	744	1,967	1,495
Repayment of debt	(350)	(500)	(413)
Increase in fiduciary liabilities, net of fiduciary receivables	358	702	568
Cash dividends to shareholders	(489)	(463)	(447)
Noncontrolling interests and other financing activities	(232)	(71)	(125)
Cash used for financing activities	(2,865)	(1,790)	(1,924)
Effect of exchange rates on cash and cash equivalents and funds held on behalf of clients	264	(549)	(235)
Net increase in cash and cash equivalents and funds held on behalf of clients	646	431	72
Cash and cash equivalents and funds held on behalf of clients at beginning of year	7,076	6,645	6,573
Cash and cash equivalents and funds held on behalf of clients at end of year	7,722	7,076	6,645
Reconciliation of cash and cash equivalents and funds held on behalf of clients:
Cash and cash equivalents	778	690	544
Cash and cash equivalents and funds held on behalf of clients classified as held for sale	43	0	0
Funds held on behalf of clients	6,901	6,386	6,101
Total cash and cash equivalents and funds held on behalf of clients	7,722	7,076	6,645
Supplemental disclosures:
Interest paid	446	351	328
Income taxes paid, net of refunds	$ 740	$ 546	$ 412