Insurance Company Subsidiary Operations - Additional Information (Details) $ in Millions			1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Jun. 10, 2024 USD ($)	Apr. 28, 2023 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2024 USD ($) Reinsurer	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded rate of premiums under insurance program				100.00%	100.00%
Ceded unpaid loss				$ 2,034	$ 2,034
Prepaid reinsurance premiums				539	539	$ 462
Increase (decrease) in loss and loss adjustment expense reserve					0
Reinsurance recoverable				2,036	2,036	125
Reserve for losses and loss adjustment expense				2,034	$ 2,034
Number of reinsurers | Reinsurer					2
Premium net written					$ 121
Net earned premiums					52
Ultimate loss reserve expense inclusive of IBNR claims				2,044	2,044	131
Hurricane Ian
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Loss reserve inclusive of IBNR claims				$ 3	$ 3		$ 3
Wright National Flood Insurance Company
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded rate of premiums under insurance program				100.00%	100.00%
Prepaid reinsurance premiums				$ 539	$ 539
Expenses and allowance rate received in premiums				29.50%	29.50%
Premiums written net					$ 773
Ceded to highly rated carriers for excess flood policies					2
Statutory capital and surplus required				$ 8	8
Statutory capital and surplus				$ 43	43	39
Statutory net Income					$ 9	$ 7
Percentage of adjusted net income				100.00%	100.00%
Maximum dividend payout that may be made without prior approval				$ 7	$ 7
Dividend paid	$ 7	$ 3
Wright National Flood Insurance Company | Maximum
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Preferred stock, dividend rate, percentage					10.00%
Wright National Flood Insurance Company | FEMA
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Premiums written net					$ 771
Quota Share Captive
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Deferred acquisitions costs				58	58
Reinsurance payable				5	5
Reserve for losses and loss adjustment expense				6	6
Premiums written net					19
Premium net written				10
Net earned premiums				22
Initial funding			$ 6
Addition to earnings					15
Ultimate loss reserve expense inclusive of IBNR claims				$ 11	11		$ 11
Captive Insurance Facility
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Maximum aggregate annual underwriting exposure					2
Maximum annual amount per occurrence					$ 6