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Municipal Bond Guarantee Insurance - Narrative (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2021 | Jan. 31, 2021 | Mar. 31, 2022 | Mar. 31, 2021 | Jun. 30, 2018 | Dec. 31, 2022 | Jan. 31, 2020 | Jul. 31, 2012
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Percentage of risk premium ceded |  |  | 60.00% |  |  |  |  |
Insurance-linked securities, term |  |  |  | 12 years | 12 years |  |  |
Insurance-linked securities, callable term |  |  |  | 5 years | 5 years |  |  |
Debt | $ 693.0 |  | $ 690.9 |  |  |  |  |
HG Global |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Collateral held in supplement trust | 852.0 |  | 836.3 |  |  |  |  |
Collateral trusts, investments and cash | 481.7 |  | 466.0 |  |  |  |  |
BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Surplus notes | 364.6 |  | 364.6 |  |  |  |  |
Interest receivable | 5.7 |  | 5.7 |  |  |  |  |
HG Global |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Surplus notes |  |  | $ 503.0 |  |  |  |  | $ 503.0
Percentage of par value of policy reinsured |  |  | 15.00% |  |  |  |  |
Percent over a target trust balance |  |  | 102.00% |  |  |  |  |
Supplement trust target |  |  | $ 603.0 |  |  |  |  |
HG Global | Series A BAM Surplus Note |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Assets Held-in-trust | 601.8 |  | $ 591.5 |  |  |  |  |
HG Global | BAM | Maximum |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Aggregate losses on ceded business |  |  |  |  |  |  | $ 75.0 |
HG Re |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Percentage of par value of policy reinsured |  |  | 15.00% |  |  |  |  |
Assets Held-in-trust | 250.2 |  | $ 244.8 |  |  |  |  |
BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Principal | 89,196.5 | $ 805.5 | 91,609.8 |  |  |  |  |
BAM | HG Global |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Interest receivable | 157.6 |  | 160.6 |  |  |  |  |
BAM | Surplus Note |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Repayments of unsecured debt | 33.8 |  |  |  |  |  |  |
Accrued interest payment on surplus notes | 9.8 |  |  |  |  |  |  |
BAM | Surplus Note | HG Global |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Debt | 364.6 |  | $ 364.6 |  |  |  |  |
BAM | Supplemental Trust |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Repayments of unsecured debt | 23.6 |  |  |  |  |  |  |
Accrued interest payment on surplus notes | $ 0.4 |  |  |  |  |  |  |
BAM | US Treasury (UST) Interest Rate | Surplus Note |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Basis spread on variable rate |  |  | 3.00% |  |  |  |  |
BAM | Fixed interest rate | Surplus Note |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Derivative, fixed interest rate (as a percent) |  |  | 8.00% |  |  |  |  |
BAM | Forecast | US Treasury (UST) Interest Rate | Surplus Note |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Effective percentage |  |  |  |  |  | 3.20% |  |
BAM | Fidus Re Ltd. |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Secured debt |  |  |  | $ 150.0 | $ 100.0 |  |  |
Aggregate losses on ceded business |  |  |  | 135.0 | 165.0 |  |  |
Premium receivable, Premium expected to be collected |  |  |  | 150.0 | 100.0 |  |  |
Percentage of quota share reinsurance agreement |  | 100.00% |  |  |  |  |  |
BAM | Fidus Re Ltd. | 2018 Covered Portfolio |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Percentage of financial guaranty policies covered |  |  | 32.00% |  |  |  |  |
BAM | Fidus Re Ltd. | 2021 Covered Portfolio |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Percentage of financial guaranty policies covered |  |  | 36.00% |  |  |  |  |
BAM | Fidus Re Ltd. | Maximum |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Aggregate losses on ceded business |  |  |  | $ 301.7 | $ 276.1 |  |  |
Fidus Re Ltd. | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Losses above retention, percentage of liability |  |  |  | 90.00% | 90.00% |  |  |

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