Losses and LAE - Reserve for Losses and LAE by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Total reserve for losses and LAE	$ 367,568	$ 426,843
Mortgage insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total reserve for losses and LAE	361,838	420,955	$ 477,747	$ 823,136
Title insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total reserve for losses and LAE	5,730	5,888
Primary case \| Mortgage insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total reserve for losses and LAE	343,336	398,874
Primary IBNR and LAE \| Mortgage insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total reserve for losses and LAE	10,005	12,169
Pool and other \| Mortgage insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Total reserve for losses and LAE	$ 8,497	$ 9,912