Losses and LAE - Additional Disclosures: Claims Development (Details) - Mortgage insurance $ in Thousands	Dec. 31, 2021 USD ($) default	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 2,592,921
2012
Claims Development [Line Items]
Incurred losses, net of reinsurance	713,057	$ 713,146	$ 713,839	$ 713,750	$ 714,783	$ 715,646	$ 720,502	$ 711,213	$ 763,969	$ 803,831
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 7
Cumulative Number of Reported Defaults | default	73,517
2013
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 398,820	399,317	399,356	400,243	402,259	404,333	401,444	405,334	$ 505,732
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 6
Cumulative Number of Reported Defaults | default	58,577
2014
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 260,254	261,377	261,507	260,098	264,620	265,891	247,074	$ 337,784
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 7
Cumulative Number of Reported Defaults | default	47,976
2015
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 182,647	184,066	183,546	183,952	178,042	198,186	$ 222,555
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 12
Cumulative Number of Reported Defaults | default	42,607
2016
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 148,349	148,640	148,811	149,753	165,440	$ 201,016
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 18
Cumulative Number of Reported Defaults | default	40,503
2017
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 126,989	130,274	133,357	151,802	$ 180,851
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 28
Cumulative Number of Reported Defaults | default	42,888
2018
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 88,252	95,534	116,634	$ 131,513
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 51
Cumulative Number of Reported Defaults | default	37,369
2019
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 109,416	136,860	$ 143,475
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 150
Cumulative Number of Reported Defaults | default	40,985
2020
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 408,809	$ 504,160
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 786
Cumulative Number of Reported Defaults | default	108,025
2021
Claims Development [Line Items]
Incurred losses, net of reinsurance	$ 156,328
Total of IBNR Liabilities Plus Expected Development on Reported Claims	$ 1,771
Cumulative Number of Reported Defaults | default	37,470