Losses and LAE - Mortgage Insurance Loss Reserves Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Loss reserve [Roll Forward]
Balance at January 1,	$ 848,413
Deduct: Paid claims and LAE related to:
Balance at December 31,	828,642	$ 848,413
Mortgage
Loss reserve [Roll Forward]
Balance at January 1,	844,107	401,273	$ 397,891
Less: Reinsurance recoverables	71,769	14,594	11,009
Balance at January 1, net of reinsurance recoverables	756,460	772,338	386,679	$ 386,882
Add: Losses and LAE incurred in respect of default notices reported and unreported in:
Current year	160,565	517,807	146,733
Prior years	(141,126)	(34,547)	(14,709)
Total incurred	19,439	483,260	132,024
Deduct: Paid claims and LAE related to:
Current year	1,112	4,148	4,220
Prior years	34,205	93,453	128,007
Total paid	35,317	97,601	132,227
Balance at end of period, net of reinsurance recoverables	756,460	772,338	386,679
Add: reinsurance recoverables	66,676	71,769	14,594
Balance at December 31,	$ 823,136	$ 844,107	$ 401,273