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Municipal Bond Guarantee (Details) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Jul. 31, 2012 USD ($) | Sep. 30, 2016 USD ($) Contract | Mar. 31, 2016 | Sep. 30, 2015 USD ($) | Sep. 30, 2016 USD ($) yr Contract | Sep. 30, 2015 USD ($) | Dec. 31, 2015 USD ($) Contract
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Pre-tax (loss) income |  | $ 20.0 |  | $ (86.9) | $ 26.4 | $ (89.0) |
Net investment income (loss) - surplus note interest |  | $ 0.0 |  | 0.0 | $ 0.0 | 0.0 |
BAM |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Municipal bond contract | Contract |  | 4,357 |  |  | 4,357 |  | 3,103
Insured Financial Obligations, Remaining Weighted Average Contract Period |  |  |  |  | 10 years 11 months |  | 12 years 10 months
Municipal bond outstanding principal |  | $ 30,470.0 |  |  | $ 30,470.0 |  | $ 22,556.0
Municipal bond outstanding interest |  | 15,258.1 |  |  | 15,258.1 |  | 11,984.4
Municipal bond debt service outstanding |  | 45,728.1 |  |  | $ 45,728.1 |  | 34,540.4
Year of U.S. Treasury Rate | yr |  |  |  |  | 1 |  |
Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Remainder of Fiscal Year |  | 1.6 |  |  | $ 1.6 |  |
Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Second Quarter |  | 1.6 |  |  | 1.6 |  |
Financial Guarantee Insurance Contracts, Premium Receivable, Premium Expected to be Collected, Third Quarter |  | 1.6 |  |  | 1.6 |  |
Financial Guarantee Insurance Contracts, Premium Receivable, Premium Expected to be Collected, Next Quarter |  | 1.6 |  |  | 1.6 |  |
Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Next Twelve Months |  | 1.5 |  |  | 1.5 |  |
Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Year Two |  | 6.3 |  |  | 6.3 |  |
Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Year Three |  | 6.0 |  |  | 6.0 |  |
Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Year Five |  | 5.4 |  |  | 5.4 |  |
Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Year Four |  | 5.7 |  |  | 5.7 |  |
Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Year Six Through Ten |  | 46.0 |  |  | 46.0 |  |
Financial Guarantee Insurance Contracts, Unearned Premium Revenue |  | 71.0 |  |  | 71.0 |  | $ 50.2
HG Global |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Partners Capital Contribution | $ 594.5 |  |  |  |  |  |
Surplus Notes | 503.0 |  |  |  |  |  |
Income (Loss) from Continuing Operations before Income Taxes, Domestic |  | $ 5.2 |  |  | $ 18.4 |  |
HG Global | Preferred Stock |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Ownership interest (as a percent) |  | 96.90% |  |  | 96.90% |  |
HG Global | Common Stock |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Ownership interest (as a percent) |  | 88.40% |  |  | 88.40% |  |
Build America Mutual |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Income (Loss) from Continuing Operations before Income Taxes, Domestic |  | $ (13.7) |  |  | $ (30.3) |  |
BAM |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Pre-tax (loss) income |  | (13.7) |  | (10.6) | (30.3) | (33.5) |
Net investment income (loss) - surplus note interest |  | (4.5) |  | (4.0) | (13.4) | (11.9) |
HG Re |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Statutory Accounting Practices, Statutory Capital and Surplus, Balance |  | 476.5 |  |  | 476.5 |  |
HG Global |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Pre-tax (loss) income |  | 5.2 |  | 5.2 | 18.4 | 13.8 |
Net investment income (loss) - surplus note interest |  | 4.5 |  | $ 4.0 | 13.4 | $ 11.9 |
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 |  |  | $ 13.4 |  |
Derivative, Fixed Interest Rate |  | 3.54% |  |  | 3.54% |  | 3.15%
Surplus Note | Build America Mutual |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |
Interest expense |  | $ 4.5 |  |  | $ 13.4 |  |
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% |  |  | 8.00% |  |

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