Insurance Company Subsidiary Operations - Additional Information (Details) $ in Millions		1 Months Ended	9 Months Ended	12 Months Ended
	Jun. 27, 2025 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2025 USD ($) Reinsurer	Dec. 31, 2024 USD ($)
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded rate of premiums under insurance program			100.00%
Ceded unpaid loss			$ 247
Prepaid reinsurance premiums			790	$ 520
Increase (decrease) in loss and loss adjustment expense reserve			0
Reinsurance recoverable			603	1,527
Unearned premiums			$ 887	577
Number of reinsurers | Reinsurer			2
Ultimate loss reserve expense inclusive of IBNR claims			$ 620	1,543
Wright National Flood Insurance Company
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded rate of premiums under insurance program			100.00%
Prepaid reinsurance premiums			$ 584
Reserve for losses and loss adjustment expense			$ 247
Expenses and allowance rate received in premiums			29.10%
Premiums written net			$ 838
Ceded to highly rated carriers for excess flood policies			3
Statutory capital and surplus required			8
Statutory capital and surplus			$ 37	44
Statutory net Income				$ 9
Percentage of adjusted net income			100.00%
Maximum dividend payout that may be made without prior approval			$ 9
Dividend paid	$ 9
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			$ 835
Quota Share Captive
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Ceded unpaid loss			356
Prepaid reinsurance premiums			206
Deferred acquisitions costs			17
Reinsurance payable			215
Reserve for losses and loss adjustment expense			373
Unearned premiums			303
Initial funding		$ 6
Addition to earnings			26
Captive Insurance Facility
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Maximum aggregate annual underwriting exposure			2
Premiums written net			$ 217