Reinsurance - Quota Share Agreement Terms (Details)	3 Months Ended
	Mar. 31, 2022
2015 QSR
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	15.00%
Loss ratio threshold for profit commissions (as a percent)	68.00%
2019 QSR
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	30.00%
Loss ratio threshold for profit commissions (as a percent)	62.00%
Cede rate, option 1 (as a percent)	25.00%
Cede rate, option 2 (as a percent)	20.00%
2020 QSR
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	12.50%
Loss ratio threshold for profit commissions (as a percent)	62.00%
Cede rate, option 1 (as a percent)	10.50%
Cede rate, option 2 (as a percent)	8.00%
2020 and 2021 QSR - 2020 NIW
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	17.50%
Loss ratio threshold for profit commissions (as a percent)	62.00%
Cede rate, option 1 (as a percent)	14.50%
Cede rate, option 2 (as a percent)	12.00%
2020 and 2021 QSR - 2021 NIW
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	17.50%
Loss ratio threshold for profit commissions (as a percent)	61.90%
Cede rate, option 1 (as a percent)	14.50%
Cede rate, option 2 (as a percent)	12.00%
2021 and 2022 QSR - 2021 NIW
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	12.50%
Loss ratio threshold for profit commissions (as a percent)	57.50%
Cede rate, option 1 (as a percent)	10.50%
Cede rate, option 2 (as a percent)	8.00%
2021 and 2022 QSR - 2022 NIW
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	15.00%
Loss ratio threshold for profit commissions (as a percent)	57.50%
Cede rate, option 1 (as a percent)	12.50%
Cede rate, option 2 (as a percent)	10.00%
2022 and 2023 QSR - 2022 NIW
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	15.00%
Loss ratio threshold for profit commissions (as a percent)	62.00%
Cede rate, option 1 (as a percent)	12.50%
Cede rate, option 2 (as a percent)	10.00%
2022 and 2023 QSR - 2023 NIW
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	15.00%
Loss ratio threshold for profit commissions (as a percent)	62.00%
Cede rate, option 1 (as a percent)	12.50%
Cede rate, option 2 (as a percent)	10.00%
Credit Union QSR
Effects of Reinsurance [Line Items]
Quota share for all policies covered (as a percent)	65.00%
Loss ratio threshold for profit commissions (as a percent)	50.00%