Segment Reporting - Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues	$ 333,857	$ 312,513	$ 974,422	$ 911,944
Net gains (losses) on investments and other financial instruments	2,174	(8,555)	(1,823)	(3,206)
Other non-operating revenue	0	868	0	868
All Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues	39,605	32,328	113,733	87,090
Operating Segments | Mortgage Insurance revenues
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues	287,572	288,257	858,578	827,955
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net gains (losses) on investments and other financial instruments	6,785	(8,838)	2,454	(3,664)
Intersegment Eliminations
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues	$ (105)	$ (102)	$ (343)	$ (305)