The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
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Name:	us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Loss reserves - Summary of Liability For Unpaid Claims And Claim Adjustment Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Effects of Reinsurance [Line Items]
Loss reserves	$ 542,528	$ 524,715
Domestic mortgage insurance
Effects of Reinsurance [Line Items]
Loss reserves	537,480	520,032	$ 530,770	$ 517,515
Other reserves
Effects of Reinsurance [Line Items]
Loss reserves	$ 5,048	$ 4,683