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CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions | Sep. 30, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Fixed income securities, available for sale, amortized cost | $ 4,657.4 | $ 4,330.0 | $ 4,131.3
Fixed income securities, available for sale, allowance for expected credit losses | 2.0 | 2.9 | 7.7
Fixed income securities, trading, amortized cost | 1,280.5 | 1,527.0 | 1,576.7
Short term investments available for sale, amortized cost | 66.5 | 93.6 | 52.4
Short-term investments, trading, amortized cost | 3.2 | 2.1 | 6.3
Catastrophe bonds, amortized cost | 1.0 | 1.6 | 5.1
Privately-held investments, available for sale, amortized cost | 25.1 | 14.7 | 0.0
Privately-held investments, trading at fair value, amortized cost | 369.2 | 494.9 | 537.7
Unpaid losses recoverable from reinsurers, allowance for expected credit losses | 11.5 | 3.7 | 3.7
Underwriting premiums receivable, allowance for expected credit losses | 24.3 | 21.0 | 25.0
Fixed income securities, trading at fair value | 1,281.3 | 1,485.7 | 1,475.5
Privately-held Investments, trading | 341.2 | 475.0 | 533.0
Privately-held Investments, available for sale | 25.3 | 14.9 | 0.0
Other investments, at fair value | 204.7 | 209.3 | 221.3
Restricted cash | 290.0 | 323.2 | 232.1
Accrued expenses and other payables | 248.4 | 214.4 | 201.8
Asset Management Arrangement |  |  |
Accrued expenses and other payables |  | 2.1 | 4.5
Related Party |  |  |
Fixed income securities, trading at fair value | 120.9 | 129.8 | 0.0
Privately-held Investments, trading | 75.4 | 112.4 | 44.8
Privately-held Investments, available for sale | 0.0 | 14.9 | 0.0
Other investments, at fair value | 38.5 | 39.8 |
Related Party | Asset Management Arrangement |  |  |
Accrued expenses and other payables | 4.0 | 2.1 | 4.5
Related Party | Management Consulting Agreement |  |  |
Accrued expenses and other payables | 1.3 | 1.2 | $ 1.3
Related Party | Dividends |  |  |
Accrued expenses and other payables | $ 20.0 | $ 0.0 |

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