Segment Reporting - Adjusted Pretax Operating Income (Loss) (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]
Net gains (losses) on investments and other financial instruments		$ (723)	$ 490
Pretax income		188,440	198,649
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Mortgage Insurance adjusted pretax operating income		194,293	209,850
Corporate, Non-Segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
All Other adjusted pretax operating income (loss)		(3,459)	(7,033)
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	[1]	(2,010)	107
Impairment of other long-lived assets and other non-operating items	[2]	(384)	(4,275)
Mortgage Insurance revenues | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Mortgage Insurance adjusted pretax operating income		194,293	209,850
Allocated corporate operating expenses	[3]	35,123	34,509
Direct depreciation expense		$ 1,940	$ 1,923

[1] 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).

[2] The non-operating item for the three months ended March 31, 2024, relates to a loss on extinguishment of debt.

[3] Includes immaterial allocated depreciation expense.