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Municipal Bond Guarantee (Details) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jun. 30, 2017 USD ($) Contract | Mar. 31, 2017 | Jun. 30, 2016 USD ($) | Jun. 30, 2017 USD ($) yr Contract | Jun. 30, 2016 USD ($) | Dec. 31, 2012 USD ($) | Dec. 31, 2016 USD ($) Contract | Jul. 31, 2012 USD ($)
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Pre-tax income (loss) | $ (0.4) |  | $ (25.1) | $ 1.0 | $ (54.8) |  |  |
Net investment income (loss) - surplus note interest | 0.0 |  | 0.0 | 0.0 | $ 0.0 |  |  |
HG Global |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Partners capital contribution |  |  |  |  |  | $ 594.5 |  |
Surplus notes |  |  |  |  |  |  |  | $ 503.0
Income (loss) from continuing operations before income taxes, domestic | $ 6.7 |  |  | $ 13.3 |  |  |  |
HG Global | Preferred Stock |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Ownership interest (as a percent) | 96.90% |  |  | 96.90% |  |  | 96.90% |
HG Global | Common Stock |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Ownership interest (as a percent) | 88.40% |  |  | 88.40% |  |  | 88.40% |
BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Surplus notes | $ 500.0 |  |  | $ 500.0 |  |  |  |
Year of U.S. Treasury rate | yr |  |  |  | 1 |  |  |  |
Municipal bond contract | Contract | 5,564 |  |  | 5,564 |  |  | 4,807 |
Remaining weighted average contract period outstanding (in years) |  |  |  | 10 years 11 months | 10 years 10 months |  |  |
Municipal bond outstanding principal | $ 37,619.7 |  |  | $ 37,619.7 |  |  | $ 33,057.3 |
Municipal bond outstanding interest | 19,013.0 |  |  | 19,013.0 |  |  | 16,396.6 |
Municipal bond debt service outstanding | 56,632.5 |  |  | 56,632.5 |  |  | 49,453.9 |
July 1, 2017 - December 31, 2017 | 4.6 |  |  | 4.6 |  |  |  |
2018 | 9.0 |  |  | 9.0 |  |  |  |
2019 | 8.6 |  |  | 8.6 |  |  |  |
2020 | 8.2 |  |  | 8.2 |  |  |  |
2021 | 7.8 |  |  | 7.8 |  |  |  |
2022 and thereafter | 71.7 |  |  | 71.7 |  |  |  |
Total gross unearned insurance premiums | 109.9 |  |  | 109.9 |  |  | $ 82.9 |
Build America Mutual |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Income (loss) from continuing operations before income taxes, domestic | (11.5) |  |  | (23.7) |  |  |  |
HG Global |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Pre-tax income (loss) | 6.7 |  | 5.9 | 13.3 | $ 13.2 |  |  |
Net investment income (loss) - surplus note interest | 4.7 |  | 4.4 | 9.5 | 8.9 |  |  |
HG Re |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Statutory capital and surplus, balance | 469.7 |  |  | 469.7 |  |  |  |
Percentage of par value of policy reinsured |  | 15.00% |  |  |  |  |  |
BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Pre-tax income (loss) | (11.5) |  | (9.0) | (23.7) | (16.6) |  |  |
Net investment income (loss) - surplus note interest | (4.7) |  | $ (4.4) | (9.5) | $ (8.9) |  |  |
BAM Management |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Partners capital contribution |  |  |  |  |  | $ 14.5 |  |
Surplus Note | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Interest income, other | $ 4.7 |  |  | $ 9.5 |  |  |  |
Derivative, fixed interest rate (as a percent) | 3.78% |  |  | 3.78% |  |  | 3.54% |
Basis points |  |  |  | 30000.00% |  |  |  |
Surplus Note | Build America Mutual |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Interest expense | $ 4.7 |  |  | $ 9.5 |  |  |  |
Combination One | Surplus Note | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Number of years of change in interest rate | yr |  |  |  | 5 |  |  |  |
Combination Two | Surplus Note | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Number of years of change in interest rate | yr |  |  |  | 3 |  |  |  |
US Treasury Rate | Surplus Note | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Basis points |  |  |  | 3.00% |  |  |  |
Fixed interest rate | Surplus Note | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Derivative, fixed interest rate (as a percent) | 8.00% |  |  | 8.00% |  |  |  |
First Quarter, year two | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
2018 | $ 2.3 |  |  | $ 2.3 |  |  |  |
Second Quarter, year two | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
2018 | 2.3 |  |  | 2.3 |  |  |  |
Third Quarter, year two | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
2018 | 2.2 |  |  | 2.2 |  |  |  |
Fourth Quarter, year two | BAM |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
2018 | 2.2 |  |  | 2.2 |  |  |  |
Series A BAM Surplus Note | HG Global |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Surplus notes | 203.0 |  |  | 203.0 |  |  |  |
Series B BAM Surplus Note | HG Global |  |  |  |  |  |  |  |
Guarantor Obligations [Line Items] |  |  |  |  |  |  |  |
Surplus notes | $ 300.0 |  |  | $ 300.0 |  |  |  |

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