Losses and LAE - Schedule of Net Incurred Losses and Paid Claims Development (Details) - Mortgage insurance $ in Thousands	Dec. 31, 2024 USD ($) Default	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 874,819
2015
Claims Development [Line Items]
Incurred losses, net of reinsurance	178,738	$ 179,344	$ 180,435	$ 182,647	$ 184,066	$ 183,546	$ 183,952	$ 178,042	$ 198,186	$ 222,555
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 2
Cumulative Number of Reported Defaults | Default	42,607
2016
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 140,962	142,521	145,267	148,349	148,640	148,811	149,753	165,440	$ 201,016
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 2
Cumulative Number of Reported Defaults | Default	40,503
2017
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 115,317	118,033	122,407	126,989	130,274	133,357	151,802	$ 180,851
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 3
Cumulative Number of Reported Defaults | Default	42,888
2018
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 66,583	70,145	75,262	88,252	95,534	116,634	$ 131,513
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 5
Cumulative Number of Reported Defaults | Default	37,369
2019
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 43,818	51,053	66,466	109,416	136,860	$ 143,475
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 9
Cumulative Number of Reported Defaults | Default	40,985
2020
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 27,266	39,584	87,213	408,809	$ 504,160
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 14
Cumulative Number of Reported Defaults | Default	108,025
2021
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 11,974	23,308	72,475	$ 156,328
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 11
Cumulative Number of Reported Defaults | Default	37,470
2022
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 24,044	71,300	$ 155,908
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 32
Cumulative Number of Reported Defaults | Default	37,738
2023
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 75,762	$ 173,076
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 0
Cumulative Number of Reported Defaults | Default	44,007
2024
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 190,355
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 1,734
Cumulative Number of Reported Defaults | Default	50,535