Reinsurance - Excess of Loss Reinsurance (Details) - USD ($) $ in Thousands						3 Months Ended	12 Months Ended
	Aug. 03, 2021	Feb. 02, 2021	Oct. 29, 2020	May 25, 2019	Oct. 30, 2018	Mar. 31, 2022	Dec. 31, 2021	Apr. 26, 2022
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						$ 190,159	$ 190,159
Remaining Excess of Loss Reinsurance Coverage	$ 398,429					398,429	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						211,142	211,142
Remaining Excess of Loss Reinsurance Coverage		$ 398,848				361,362	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						275,172	275,204
Remaining Excess of Loss Reinsurance Coverage			$ 412,917			196,552	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						183,807	183,917
Remaining Excess of Loss Reinsurance Coverage				$ 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						165,179	165,365
Remaining Excess of Loss Reinsurance Coverage					$ 318,636	$ 218,343	$ 218,343
Home Re 2022-1 | Subsequent Event
Effects of Reinsurance [Line Items]
Remaining Excess of Loss Reinsurance Coverage								$ 473,600