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Amount of the reinsurer's funds held on its behalf by the ceding insurer, including funds held in trust, under reinsurance treaties or contracts with the assuming insurer as security for the payment of the obligations thereunder.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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The total amount of other operating income, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operation.

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Percentage of par value of policy reinsured.

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Municipal Bond Guarantee Insurance - Narrative (Details)	3 Months Ended
	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)	Jul. 01, 2024 USD ($)	Jun. 30, 2024
Guarantor Obligations [Line Items]
Member surplus contributions, insurance premium charges, percentage	55.00%
Direct	$ 6,700,000	$ 10,500,000
Gross earned premiums	8,200,000	7,800,000
Assets held-in-trust	976,200,000		$ 950,100,000
Collateral trusts, investments and cash	296,700,000		289,400,000
Surplus notes	300,900,000		300,900,000
Interest receivable	15,200,000		7,700,000
Debt	676,100,000		562,500,000
Interest income from BAM Surplus Notes	7,500,000	0
Operating Segments \| Financial Guarantee (HG Global)
Guarantor Obligations [Line Items]
Debt	147,500,000		147,400,000
Interest income from BAM Surplus Notes	7,500,000	0
Notes receivable, fair value disclosure	389,200,000		381,700,000	$ 387,400,000
BAM Surplus Notes
Guarantor Obligations [Line Items]
Distribution received	$ 0	$ 26,200,000
BAM Surplus Notes \| Surplus Notes
Guarantor Obligations [Line Items]
Basis spread on variable rate	3.00%
Stated margin				10.00%	8.20%
Debt	$ 300,900,000		300,900,000
Interest receivable	$ 202,300,000		$ 194,800,000
BAM Surplus Notes \| Surplus Notes \| Discount Rate
Guarantor Obligations [Line Items]
Debt instrument, measurement input	0.0800		0.0810
Subsidiary - HG Global
Guarantor Obligations [Line Items]
Purchase of surplus notes	$ 503,000,000
Percentage of risk premium ceded	60.00%
Renegotiation period	5 years
Percent over a target trust balance	102.00%
Subsidiary - HG Global \| Regulation 114
Guarantor Obligations [Line Items]
Assets held-in-trust	$ 363,400,000		$ 352,100,000
Supplement trust target	603,000,000
Subsidiary - HG Global \| Supplemental Trust
Guarantor Obligations [Line Items]
Assets held-in-trust	$ 612,800,000		$ 598,000,000
Subsidiary - HG Global \| Maximum
Guarantor Obligations [Line Items]
Percentage of par value of policy reinsured	15.00%
Variable Interest Entity, Primary Beneficiary - Build America Mutual Assurance Company \| Fidus Re Ltd.
Guarantor Obligations [Line Items]
Reinsured amount	$ 125,000,000