Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended	6 Months Ended		12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2025 USD ($) Segment	Jun. 30, 2025 Segment	Dec. 31, 2025 USD ($) Segment	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of reportable segments | Segment		2	3	2
Change in accounting principle, accounting standards update, adopted		true		true
Accounting Standards Update [Extensible Enumeration]				us-gaap:AccountingStandardsUpdate202309Member
Amount recorded additional gain from settlement of contingent payments					$ 29,000,000
Change in accounting principle, accounting standards update, adoption date		Dec. 31, 2025		Dec. 31, 2025
Accumulated impairment losses		$ 0		$ 0
Goodwill impairment loss				0	0	$ 0
Gain on Disposition of Assets				(2,000,000)	31,000,000	$ 143,000,000
Carrying value of fixed-rate borrowings		7,032,000,000		7,032,000,000	2,839,000,000
Long-term Debt, Fair Value		$ 7,002,000,000		7,002,000,000	$ 2,602,000,000
Revolving and term loan				$ 632,000,000
Purchased Customer Accounts and Other
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Finite-Lived Intangible Asset, Useful Life		15 years		15 years
Third-party Claims Administration and Adjusting Services Businesses | Services
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Gains recognized on sales of businesses	$ 135,000,000
Minimum
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Property, Plant and Equipment, Useful Life		3 years		3 years
Maximum
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Property, Plant and Equipment, Useful Life		40 years		40 years