Segment Reporting - Revenue and Other Segment Information (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues		$ 318,114	$ 319,418
Provision for losses		15,167	(7,034)
Policy acquisition costs		6,388	6,794
Interest expense		22,499	29,046
Net gains (losses) on investments and other financial instruments		(723)	490
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Adjusted pretax operating income		194,293	209,850
Operating Segments | Mortgage Insurance revenues
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total revenues		284,298	285,023
Provision for losses		15,340	(6,886)
Policy acquisition costs		6,388	6,794
Direct other operating expenses		16,567	17,270
Allocated corporate operating expenses	[1]	35,123	34,509
Interest expense		16,489	23,333
Other segment items		98	153
Adjusted pretax operating income		194,293	209,850
Direct depreciation expense		$ 1,940	$ 1,923
Loss Ratio	[2]	6.60%	(2.90%)
Expense Ratio	[3]	24.80%	25.00%
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	[4]	$ (2,010)	$ 107

[1] Includes immaterial allocated depreciation expense.

[2] Calculated as provision for losses expressed as a percentage of net premiums earned.

[3] Calculated as operating expenses (which consist of policy acquisition costs, direct other operating expenses and allocated corporate operating expenses) expressed as a percentage of net premiums earned.

[4] Excludes net gains (losses) on investments and other financial instruments that are attributable to our Mortgage Conduit business, which are included in All Other adjusted pretax operating income (loss).