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Municipal Bond Guarantee (Details) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jul. 31, 2012 USD ($) | Mar. 31, 2016 USD ($) yr Contract | Mar. 31, 2015 USD ($) | Dec. 31, 2015 USD ($) Contract
Guarantor Obligations [Line Items] |  |  |  |
Pre-tax (loss) income |  | $ 11.5 | $ 0.5 |
Net investment income (loss) - surplus note interest |  | $ 0.0 | 0.0 |
BAM |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Municipal bond contract | Contract |  | 3,422 |  | 3,103
Insured Financial Obligations, Remaining Weighted Average Contract Period |  | 12 years 8 months |  | 12 years 10 months
Municipal bond outstanding principal |  | $ 24,641.6 |  | $ 22,556.0
Municipal bond outstanding interest |  | 12,711.9 |  | 11,984.4
Municipal bond debt service outstanding |  | 37,353.5 |  | 34,540.4
Financial Guarantee Insurance Contracts, Unearned Premium Revenue |  | $ 55.8 |  | $ 50.2
Year of U.S. Treasury Rate | yr |  | 1 |  |
HG Global |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Partners Capital Contribution | $ 594.5 |  |  |
Surplus Notes | 503.0 |  |  |
Income (Loss) from Continuing Operations before Income Taxes, Domestic |  | $ 7.3 |  |
HG Global | Preferred Stock |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Ownership interest (as a percent) |  | 96.90% |  |
HG Global | Common Stock |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Ownership interest (as a percent) |  | 88.40% |  |
Build America Mutual |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Income (Loss) from Continuing Operations before Income Taxes, Domestic |  | $ (7.6) | (8.8) |
HG Re |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Statutory Accounting Practices, Statutory Capital and Surplus, Balance |  | 467.2 |  |
HG Global |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Pre-tax (loss) income |  | 7.3 |  |
Net investment income (loss) - surplus note interest |  | $ 4.5 |  |
HG Global | HG Global |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Pre-tax (loss) income |  |  | 5.5 |
Net investment income (loss) - surplus note interest |  |  | 4.0 |
BAM Management |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Partners Capital Contribution | $ 14.5 |  |  |
Surplus Note | BAM |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Basis points |  | 3.00% |  |
Interest Income, Other |  | $ 4.5 |  |
Derivative, Fixed Interest Rate |  | 3.54% |  | 3.15%
Surplus Note | Build America Mutual |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Interest income (expense), surplus notes |  | $ 4.5 | $ 4.0 |
Combination One [Member] | Surplus Note | BAM |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Number of years of change in interest rate | yr |  | 5 |  |
Combination Two [Member] | Surplus Note | BAM |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Number of years of change in interest rate | yr |  | 3 |  |
Financial Guarantee [Member] |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Percentage of par value of policy reinsured |  | 15.00% |  |
Fixed interest rate [Member] | Surplus Note | BAM |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |
Derivative, Fixed Interest Rate |  | 8.00% |  |

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