Municipal Bond Guarantee Insurance - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2022	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018	Jan. 01, 2025	Dec. 31, 2023	Mar. 31, 2021	Jun. 30, 2018	Jul. 31, 2012
Guarantor Obligations [Line Items]
Percentage of risk premium ceded		60.00%		60.00%
Insurance-linked securities, term						12 years	12 years	12 years
Insurance-linked securities, callable term						7 years	5 years	5 years
HG Global
Guarantor Obligations [Line Items]
Collateral held in supplement trust	$ 856,900,000	$ 892,400,000		$ 892,400,000		$ 856,900,000
Collateral trusts, investments and cash	503,300,000	525,700,000		525,700,000		503,300,000
BAM
Guarantor Obligations [Line Items]
Surplus notes	340,000,000	340,000,000		340,000,000		340,000,000
Interest receivable	13,600,000	26,700,000		26,700,000		13,600,000
Series A BAM Surplus Note | BAM
Guarantor Obligations [Line Items]
Interest receivable	157,900,000	171,000,000		171,000,000		157,900,000
HG Global
Guarantor Obligations [Line Items]
Surplus notes		$ 503,000,000		$ 503,000,000									$ 503,000,000
Percentage of par value of policy reinsured		15.00%		15.00%
Percent over a target trust balance				102.00%
Supplement trust target		$ 603,000,000		$ 603,000,000
HG Global | Series A BAM Surplus Note
Guarantor Obligations [Line Items]
Assets Held-in-trust	568,300,000	$ 585,600,000		585,600,000		568,300,000
HG Global | BAM | Maximum
Guarantor Obligations [Line Items]
Reinsurance, Excess Retention, Amount Reinsured, Per Life				$ 125,000,000
HG Re
Guarantor Obligations [Line Items]
Percentage of par value of policy reinsured		15.00%		15.00%
Assets Held-in-trust	288,600,000	$ 306,800,000		$ 306,800,000		288,600,000
BAM | Surplus Note
Guarantor Obligations [Line Items]
Repayments of unsecured debt	36,000,000	$ 0	$ 0	$ 0	$ 0
Accrued interest payment on surplus notes	10,400,000					10,400,000
BAM | Supplemental Trust
Guarantor Obligations [Line Items]
Repayments of unsecured debt	24,600,000
Accrued interest payment on surplus notes	1,000,000					1,000,000
BAM | US Treasury (UST) Interest Rate | Surplus Note
Guarantor Obligations [Line Items]
Basis spread on variable rate				3.00%
BAM | Forecast | US Treasury (UST) Interest Rate | Surplus Note
Guarantor Obligations [Line Items]
Effective percentage										7.70%
BAM | Forecast | Fixed interest rate | Surplus Note
Guarantor Obligations [Line Items]
Derivative, fixed interest rate (as a percent)									8.00%
BAM | Fidus Re Ltd.
Guarantor Obligations [Line Items]
Secured debt	$ 150,000,000					150,000,000					$ 150,000,000	$ 100,000,000
Reinsurance, Limit on Total Reimbursement						150,000,000	$ 150,000,000	$ 100,000,000
Percentage of financial guaranty policies covered				31.00%
BAM | Fidus Re Ltd. | 2018 Covered Portfolio
Guarantor Obligations [Line Items]
Percentage of financial guaranty policies covered				26.00%
BAM | Fidus Re Ltd. | 2021 Covered Portfolio
Guarantor Obligations [Line Items]
Percentage of financial guaranty policies covered				30.00%
BAM | Fidus Re Ltd. | Maximum
Guarantor Obligations [Line Items]
Reinsurance, Excess Retention, Amount Reinsured, Per Life						276,700,000	301,700,000	276,100,000
BAM | Fidus Re Ltd. | Minimum
Guarantor Obligations [Line Items]
Reinsurance, Excess Retention, Amount Reinsured, Per Life						$ 110,000,000	$ 135,000,000	$ 165,000,000
Fidus Re Ltd. | BAM
Guarantor Obligations [Line Items]
Percentage of par value of policy reinsured						90.00%	90.00%	90.00%