Reinsurance - Excess of Loss Reinsurance (Details) - USD ($) $ in Thousands							9 Months Ended	12 Months Ended
	Apr. 26, 2022	Aug. 03, 2021	Feb. 02, 2021	Oct. 29, 2020	May 25, 2019	Oct. 30, 2018	Sep. 30, 2022	Dec. 31, 2021
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							$ 325,589
Excess of loss reinsurance coverage, initial and remaining	$ 473,575						473,575
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							190,135	$ 190,159
Excess of loss reinsurance coverage, initial and remaining		$ 398,429					367,702	398,429
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							211,117	211,142
Excess of loss reinsurance coverage, initial and remaining			$ 398,848				306,243	387,830
Home Re 2020-1
Effects of Reinsurance [Line Items]
Term of mortgage insurance-linked notes				10 years
Initial first layer retention				$ 275,283
Remaining first layer retention							275,154	275,204
Excess of loss reinsurance coverage, initial and remaining				$ 412,917			133,120	234,312
Home Re 2019-1
Effects of Reinsurance [Line Items]
Term of mortgage insurance-linked notes					10 years
Initial first layer retention					$ 185,730
Remaining first layer retention							183,691	183,917
Excess of loss reinsurance coverage, initial and remaining					$ 315,739		208,146	208,146
Home Re 2018-1
Effects of Reinsurance [Line Items]
Term of mortgage insurance-linked notes						10 years
Initial first layer retention						$ 168,691
Remaining first layer retention							165,028	165,365
Excess of loss reinsurance coverage, initial and remaining						$ 318,636	$ 162,305	$ 218,343