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Municipal Bond Guarantee Insurance (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of par value of policy reinsured |  |  |  |  | 15.00% |  |  |  |  |  | 15.00% |  |
Pre-tax loss | $ 134.2 | $ 55.3 | $ 3.6 | $ 151.8 | $ (50.8) | $ 135.1 | $ 37.6 | $ 140.9 | $ 344.9 |  | $ 262.8 |  | $ 98.0
Net investment income (loss) - surplus note interest |  |  |  |  |  |  |  |  | 0 |  | 0 |  |
BAM |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Statutory capital and surplus | 469.0 |  |  |  |  |  |  |  | 469.0 |  |  |  |
Municipal bond contract | 218 |  |  |  | 3 |  |  |  | 218 |  | 3 |  |
Insured Financial Obligations with Credit Deterioration, Remaining Weighted Average Contract Period |  |  |  |  |  |  |  |  | 13 years 9 months 21 days |  | 10 years 4 months 24 days |  |
Municipal bond outstanding principal | 4,703.7 |  |  |  | 25.8 |  |  |  | 4,703.7 |  | 25.8 |  |
Municipal bond outstanding interest | 3,264.4 |  |  |  | 8.9 |  |  |  | 3,264.4 |  | 8.9 |  |
Financial Guarantee Insurance Contracts, Unearned Premium Revenue | 13.2 |  |  |  | 0.1 |  |  |  | 13.2 |  | 0.1 |  |
White Mountains |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Capital contributions |  |  |  |  |  |  |  |  |  |  | 594.5 |  |
HG Global |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Capital contributions |  |  |  |  |  | 600.0 |  |  |  |  |  |  |
Ownership interest (as a percent) | 97.30% |  |  |  |  |  |  |  | 97.30% |  |  |  |
Surplus notes | 503.0 |  |  |  | 503.0 |  |  |  | 503.0 |  | 503.0 |  |
Percentage of par value of policy reinsured | 15.00% |  |  |  |  |  |  |  | 15.00% |  |  |  |
BAM Management |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Capital contributions |  |  |  |  |  |  |  |  |  |  | 14.5 |  |
Preferred stocks | HG Global |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest (as a percent) | 97.30% |  |  |  | 97.30% |  |  |  | 97.30% |  | 97.30% |  |
Common Stock | HG Global |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest (as a percent) | 88.70% |  |  |  | 88.70% |  |  |  | 88.70% |  | 88.70% |  |
BAM |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Surplus notes | 503.0 |  |  |  |  |  |  |  | 503.0 |  |  |  |
Interest income (expense), surplus notes |  |  |  |  |  |  |  |  | (40.2) | [1] | (18.4) | [1] |
HG Re |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Statutory capital and surplus | 436.9 |  |  |  | 412.0 |  |  |  | 436.9 |  | 412.0 |  |
HG Global |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of par value of policy reinsured | 15.00% |  |  |  |  |  |  |  | 15.00% |  |  |  |
Pre-tax loss |  |  |  |  |  |  |  |  | 38.1 |  | 14.2 |  |
Net investment income (loss) - surplus note interest |  |  |  |  |  |  |  |  | 40.2 |  | 18.4 |  |
Non-controlling Interests | BAM |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Pre-tax loss |  |  |  |  |  |  |  |  | (78.6) | [1] | (36.3) | [1] |
Surplus Note | HG Global |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Interest Receivable | $ 58.6 |  |  |  |  |  |  |  | $ 58.6 |  |  |  |
[1] | BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes surplus notes and is not reduced by accruals of interest expense on the surplus notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the New York Department of Financial Services.

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