Business Combinations and Asset Acquisitions (Details) - USD ($)		6 Months Ended	9 Months Ended
	Jul. 31, 2024	Jun. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Aug. 02, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition, Percentage of Voting Interests Acquired					60.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	$ 8,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	312,000,000
Goodwill, Acquired During Period	350,000,000	$ 9,000,000	$ 350,000,000
Goodwill, Foreign Currency Translation Gain (Loss)			14,000,000
Business Combination Recognized identifiable Assets Acquired and Liabilities Assumed Advanced Commissions	(49,000,000)
Business Combination Recognized identifiable Assets Acquired and Liabilities Assumed Premium Payable	(6,000,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities	(74,000,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	(20,000,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilites Assumed,Redeemable noncontrolling interest	179,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilites Assumed,Redeemable noncontrolling interestNonredeemable noncontrolling interests	(148,000,000)
Redeemable Noncontrolling Interest, Equity, Carrying Amount			204,000,000	$ 22,000,000		$ 17,000,000	$ 20,000,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual			8,000,000
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual			(2,000,000)
Business Acquisition, Pro Forma Revenue			362,000,000	238,000,000
Business Acquisition, Pro Forma Net Income (Loss)			18,000,000	$ 4,000,000
Business Combination, Acquisition Related Costs			$ 26,000,000
Business Combination, Redeemable Noncontrolling Percentage			40.00%
Business Combination, Consideration Paid in Cash	252,000,000
Business Combination, Total Consideration	281,000,000
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedShortTermInvestments	29,000,000
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCommissionReceivable	5,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	11,000,000
Finite-Lived Intangible Assets, Gross	$ 312,000,000
Finite-Lived Intangible Asset, Expected Amortization, Remainder of Fiscal Year			$ 8,000,000
Finite-Lived Intangible Asset, Expected Amortization, Year Three			31,000,000
Finite-Lived Intangible Asset, Expected Amortization, Year Four			31,000,000
Finite-Lived Intangible Asset, Expected Amortization, Year Two			31,000,000
Finite-Lived Intangible Asset, Expected Amortization, Year Five			31,000,000
Finite-Lived Intangible Assets, Net			586,000,000			$ 292,000,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years 6 months
Thereafter			174,000,000
Business Combination paid in Common Shares	$ 29,000,000
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAsset	$ 43,000,000
Customer Relationships And Trademarks
Finite-Lived Intangible Assets, Net			306,000,000
Customer Relationships
Finite-Lived Intangible Asset, Useful Life	10 years
Finite-Lived Intangible Assets, Gross	$ 303,000,000
Trademarks
Finite-Lived Intangible Asset, Useful Life	10 years
Finite-Lived Intangible Assets, Gross	$ 8,000,000
Common Stock [Member]
Business Combination, Consideration Transferred			2,216,023
Insurance Distribution
Goodwill, Acquired During Period			$ 350,000,000