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Income Taxes - Valuation Allowance (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Valuation Allowance [Line Items] |  |  |
Valuation allowance | $ 92.3 | $ 97.4 |
Change in valuation allowance | 2.4 | 29.2 | $ (63.6)
Income tax expense (benefit) | 38.6 | (20.5) | $ 29.3
U.S. losses and other federal deferred tax benefits |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance | 42.9 | 46.5 |
Net operating losses in Luxembourg subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance | 25.2 |  |
Net Operating Losses in Israel Subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance | 21.9 | 20.0 |
Net Operating Losses in United Kingdom Subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance | 2.3 |  |
Luxembourg | U.S. losses and other federal deferred tax benefits |  |  |
Valuation Allowance [Line Items] |  |  |
Change in valuation allowance | (1.6) | 4.2 |
United Kingdom | Net Operating Losses in United Kingdom Subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Change in valuation allowance | (1.9) | 1.0 |
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 | 1.9 | 2.7 |
Subsidiaries | Luxembourg | Net operating losses in Luxembourg subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance |  | 26.8 |
Subsidiaries | United Kingdom | Net operating losses in Luxembourg subsidiaries |  |  |
Valuation Allowance [Line Items] |  |  |
Valuation allowance |  | 4.1 |
Guilford Holdings, Inc. | United States |  |  |
Valuation Allowance [Line Items] |  |  |
Change in valuation allowance | (3.6) |  |
Income tax expense (benefit) |  | 14.9 |
BAM | United States |  |  |
Valuation Allowance [Line Items] |  |  |
Income tax expense (benefit) | 7.8 | 4.5 |
BAM | United States | MSC |  |  |
Valuation Allowance [Line Items] |  |  |
Income tax expense (benefit) | (7.5) | (9.7) |
BAM | United States | Foreign Tax Credits |  |  |
Valuation Allowance [Line Items] |  |  |
Income tax expense (benefit) | $ (0.8) | $ 1.9 |

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