CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Cash flows from operating activities:
Net income before non-controlling interests	$ 799	$ 791
Adjustments to reconcile net income before non-controlling interests to net cash provided by operating activities:
Amortization	196	131
Depreciation	37	33
Non-cash stock-based compensation	76	77
Change in estimated acquisition earn-out payables	18	(9)
Mark-to-market of escrow liability	8
Deferred income taxes	18	(11)
Net loss/(gain) on sales/disposals of investments, businesses, fixed assets and customer accounts	2	(29)
Payments on acquisition earn-outs in excess of original estimated payables	(1)	(35)
Other	5	3
Changes in operating assets and liabilities, net of effect from acquisitions and divestitures:
Commissions, fees and other receivables (increase) decrease	(59)	(119)
Reinsurance recoverable (increase) decrease	1,190	(1,911)
Prepaid reinsurance premiums (increase) decrease	8	(77)
Other assets (increase) decrease	(23)	(81)
Losses and loss adjustment reserve increase (decrease)	(1,188)	1,913
Unearned premiums increase (decrease)	15	163
Accounts payable increase (decrease)	(95)	(9)
Accrued expenses and other liabilities increase (decrease)	(41)	(17)
Other liabilities increase (decrease)	41
Net cash provided by operating activities	1,006	813
Cash flows from investing activities:
Additions to fixed assets	(48)	(62)
Payments for businesses acquired, net of cash acquired	(7,659)	(118)
Proceeds from sales of businesses, fixed assets and customer accounts	10	60
Other investing activities	(4)	1
Net cash used in investing activities	(7,701)	(119)
Cash flows from financing activities:
Fiduciary receivables and liabilities, net	(145)	83
Payments on acquisition earn-outs	(77)	(100)
Proceeds from long-term debt	4,192	599
Payments on long-term debt	(206)	(700)
Deferred debt issuance costs	(37)	(5)
Borrowings on revolving credit facility	450	150
Payments on revolving credit facility	(500)	(250)
Proceeds from issuance of common stock, net of expenses	4,315
Issuances of common stock for employee stock benefit plans	43	44
Repurchase shares to fund tax withholdings for non-cash stock-based compensation	(42)	(54)
Cash dividends paid	(137)	(111)
Other financing activities	(5)	3
Net cash provided by (used in) financing activities	7,851	(341)
Effect of foreign exchange rate changes on cash and cash equivalents inclusive of fiduciary cash	66	45
Net increase in cash, cash equivalents and restricted cash inclusive of fiduciary cash	1,222	398
Cash, cash equivalents and restricted cash inclusive of fiduciary cash at beginning of period	2,502	2,303
Net increase in cash, cash equivalents and restricted cash inclusive of fiduciary cash at end of period	$ 3,724	$ 2,701