Losses and LAE - Mortgage Insurance Loss Reserves Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Loss reserve [Roll Forward]
Balance at beginning of year	$ 426,843
Deduct: Paid claims and LAE related to:
Balance at end of year	370,148	$ 426,843
Mortgage Insurance
Loss reserve [Roll Forward]
Balance at beginning of year	420,955	823,136	$ 844,107
Less: Reinsurance recoverables	24,727	66,676	71,769
Balance at beginning of year, net of reinsurance recoverables	339,849	396,228	756,460	$ 772,338
Add: Losses and LAE incurred in respect of default notices reported and unreported in:
Current year	178,665	160,049	160,565
Prior years	(220,801)	(499,423)	(141,126)
Total incurred	(42,136)	(339,374)	19,439
Deduct: Paid claims and LAE related to:
Current year	246	499	1,112
Prior years	13,997	20,359	34,205
Total paid	14,243	20,858	35,317
Balance at end of period, net of reinsurance recoverables	339,849	396,228	756,460
Add: reinsurance recoverables	25,074	24,727	66,676
Balance at end of year	$ 364,923	$ 420,955	$ 823,136