Reinsurance - Excess of Loss Reinsurance (Details) - USD ($) $ in Thousands										9 Months Ended	12 Months Ended
	Jun. 01, 2025	Mar. 01, 2025	Apr. 01, 2024	Oct. 23, 2023	Apr. 01, 2023	Apr. 26, 2022	Apr. 01, 2022	Aug. 03, 2021	Feb. 02, 2021	Sep. 30, 2025	Dec. 31, 2024
2025 Traditional XOL
Effects of Reinsurance [Line Items]
Amortization period excess of loss reinsurance coverage	10 years
Excess of loss reinsurance coverage, initial and remaining	$ 160,000
2024 Traditional XOL
Effects of Reinsurance [Line Items]
Amortization period excess of loss reinsurance coverage			10 years
Initial First Layer Retention			$ 125,016
Remaining First Layer Retention										$ 124,777	$ 125,016
Excess of loss reinsurance coverage, initial and remaining			$ 187,220							187,220	187,220
2023 Traditional XOL
Effects of Reinsurance [Line Items]
Amortization period excess of loss reinsurance coverage					10 years
Initial First Layer Retention					$ 70,578
Remaining First Layer Retention										69,538	70,401
Excess of loss reinsurance coverage, initial and remaining					$ 96,942					71,718	91,404
2022 Traditional XOL
Effects of Reinsurance [Line Items]
Amortization period excess of loss reinsurance coverage							10 years
Initial First Layer Retention							$ 82,523
Remaining First Layer Retention										79,012	81,112
Excess of loss reinsurance coverage, initial and remaining							$ 142,642			103,875	124,344
2020 Traditional XOL
Effects of Reinsurance [Line Items]
Amortization period excess of loss reinsurance coverage		10 years
Initial First Layer Retention		$ 68,343
Remaining First Layer Retention										68,343
Excess of loss reinsurance coverage, initial and remaining		$ 250,592								$ 250,592
Excess of Loss Reinsurance Transactions, Home Re Transactions
Effects of Reinsurance [Line Items]
Percent of reinsurance coverage threshold, option to terminate (as a percent)										10.00%
Home Re 2023-1
Effects of Reinsurance [Line Items]
Term of mortgage insurance-linked notes				10 years
Initial First Layer Retention				$ 272,961
Remaining First Layer Retention										$ 268,358	272,269
Excess of loss reinsurance coverage, initial and remaining				$ 330,277						$ 250,932	299,325
Reinsurance Retention Policy, Funding Percentage				97.00%						96.00%
Home Re 2022-1
Effects of Reinsurance [Line Items]
Term of mortgage insurance-linked notes						12 years 6 months
Initial First Layer Retention						$ 325,589
Remaining First Layer Retention										$ 320,026	322,566
Excess of loss reinsurance coverage, initial and remaining						$ 473,575				$ 229,121	305,639
Reinsurance Retention Policy, Funding Percentage						100.00%				100.00%
Home Re 2021-2
Effects of Reinsurance [Line Items]
Term of mortgage insurance-linked notes								12 years 6 months
Initial First Layer Retention								$ 190,159
Remaining First Layer Retention										$ 187,230	188,211
Excess of loss reinsurance coverage, initial and remaining								$ 398,429		$ 98,270	132,424
Reinsurance Retention Policy, Funding Percentage								100.00%		98.00%
Home Re 2021-1
Effects of Reinsurance [Line Items]
Term of mortgage insurance-linked notes									12 years 6 months
Initial First Layer Retention									$ 211,159
Remaining First Layer Retention										$ 209,534	210,027
Excess of loss reinsurance coverage, initial and remaining									$ 398,848	$ 42,507	$ 92,019
Reinsurance Retention Policy, Funding Percentage									100.00%	100.00%