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Income Taxes (Valuation Allowance) (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Valuation allowance | $ 146.6 |  |  |  | $ 165.4 |  |  |  | $ 146.6 | $ 165.4 |
Change in valuation allowance |  |  |  |  |  |  |  |  | (9.1) | 19.4 | $ 35.7
Income Tax Expense (Benefit) | (23.0) | $ (6.7) | $ (6.0) | $ (9.7) | (1.0) | $ (1.6) | $ (2.2) | $ 4.6 | (45.4) | (0.2) | $ (14.8)
Net operating losses in Luxembourg subsidiaries |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Valuation allowance | 24.4 |  |  |  |  |  |  |  | 24.4 |  |
U.S. losses and other federal deferred tax benefits |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Valuation allowance | 117.3 |  |  |  | 131.5 |  |  |  | 117.3 | 131.5 |
Net Operating Losses in Israel Subsidiaries [Member] |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Valuation allowance | 4.6 |  |  |  | 5.5 |  |  |  | 4.6 | 5.5 |
Net Operating Losses in UK Subsidiaries [Member] [Member] |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Valuation allowance | 0.3 |  |  |  |  |  |  |  | 0.3 |  |
Non-US | Net operating losses in Luxembourg subsidiaries |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  |  | 0.3 |
Non-US | Net Operating Losses in Israel Subsidiaries [Member] |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  | 1.1 | 3.0 |
UNITED KINGDOM | UNITED STATES |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  | 0.1 |  |
Subsidiaries | Luxembourg | Net operating losses in Luxembourg subsidiaries |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Valuation allowance |  |  |  |  | 28.3 |  |  |  |  | 28.3 |
Subsidiaries | NETHERLANDS | Net operating losses in Luxembourg subsidiaries |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Valuation allowance |  |  |  |  | $ 0.1 |  |  |  |  | 0.1 |
Non-US | UNITED STATES |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  | 2.8 |  |
Guilford Holdings, Inc. | UNITED STATES |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  | 17.1 | 9.1 |
BAM |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  | 3.6 | 6.3 |
Income Tax Expense (Benefit) |  |  |  |  |  |  |  |  | (11.0) | (8.7) |
Houston General Insurance [Member] |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  | 0.1 | (0.5) |
Star & Shield Insurance Exchange [Member] |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  | (6.9) | $ 1.2 |
Continuing Operations [Member] |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Change in valuation allowance |  |  |  |  |  |  |  |  | (21.4) |  |
Stock Compensation Plan [Member] |  |  |  |  |  |  |  |  |  |  |
Valuation Allowance [Line Items] |  |  |  |  |  |  |  |  |  |  |
Operating Loss Carryforwards | $ 9.9 |  |  |  |  |  |  |  | $ 9.9 |  |

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