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Income Taxes - Valuation Allowance (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Valuation Allowance [Line Items] |  |  |
Valuation allowance | $ 94.3 | $ 85.6 |
Change in valuation allowance | 19.6 | 2.0 | $ 26.6
Income tax expense (benefit) | 41.4 | 44.4 | $ (14.8)
U.S. losses and other federal deferred tax benefits |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance | 56.6 | 38.2 |
Net operating losses in Israel subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance | 20.4 | 21.9 |
Luxembourg | U.S. losses and other federal deferred tax benefits |  |  |
Valuation Allowance [Line Items] |  |  |
Change in valuation allowance | 9.2 | 1.6 |
United Kingdom | Net operating losses in United Kingdom subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Change in valuation allowance | 1.0 | 3.1 |
United States | Net operating losses in US branches |  |  |
Valuation Allowance [Line Items] |  |  |
Income tax expense (benefit) |  | 0.6 |
Israel | Net operating losses in Israel subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Change in valuation allowance | 1.5 | 1.9 |
Subsidiaries | Luxembourg | Net operating losses in Luxembourg subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance | 16.0 | 25.2 |
Subsidiaries | United Kingdom | Net operating losses in Luxembourg subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance | 1.3 | 0.3 |
Guilford Holdings, Inc. | United States |  |  |
Valuation Allowance [Line Items] |  |  |
Change in valuation allowance | 7.8 |  |
Income tax expense (benefit) |  | (3.6) |
BAM | United States |  |  |
Valuation Allowance [Line Items] |  |  |
Income tax expense (benefit) | 17.5 | 7.8 |
BAM | United States | MSC |  |  |
Valuation Allowance [Line Items] |  |  |
Income tax expense (benefit) | (10.9) | $ (7.5) |
BAM | United States | Foreign Tax Credits |  |  |
Valuation Allowance [Line Items] |  |  |
Income tax expense (benefit) | $ 4.0 |  |

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