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Investment Securities - Significant Unobservable Inputs (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Investments in trading securities | $ 178.9 | $ 118.3 | $ 118.4
Kudu |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Investments in trading securities |  | 118.2 |
PassportCard/DavidShield |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Investments in trading securities |  | 15.0 |
Other long-term investments | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, fair value | 46.7 | $ 27.6 |
TIG Advisors LLC, TK Partners LLC, Third Eye Capital Management And Douglass Winthrop Advisors | Kudu |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Investments in trading securities | $ 223.4 |  |
Measurement Input, Discount Rate | Kudu's Participation Contracts | Standard Poors NR Rating |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, pretax discount rate | 0.20 | 0.20 |
Measurement Input, Discount Rate | Kudu's Participation Contracts | Standard Poors NR Rating | Minimum |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) | 18.00% | 18.00% |
Measurement Input, Discount Rate | Kudu's Participation Contracts | Standard Poors NR Rating | Maximum |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) | 23.00% | 23.00% |
Measurement Input, Discount Rate | PassportCard/DavidShield | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) | 23.00% | 23.00% |
Measurement Input, Discount Rate | Elementum Holdings, L.P. | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) | 17.00% | 17.00% |
Measurement Input, Discount Rate | Private debt investments | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) | 8.00% |  |
Measurement Input, Discount Rate | Private debt investments | Standard Poors NR Rating | Minimum |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) |  | 4.00% |
Measurement Input, Discount Rate | Private debt investments | Standard Poors NR Rating | Maximum |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) |  | 8.00% |
Measurement Input, Discount Rate | Other long-term investments | Standard Poors NR Rating | Minimum |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) |  | 20.00% |
Measurement Input, Discount Rate | Other long-term investments | Standard Poors NR Rating | Maximum |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Fair value, discount rate (as a percent) |  | 24.00% |
Measurement Input, Long-term Revenue Growth Rate | PassportCard/DavidShield | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Terminal revenue growth rate (as a percent) | 4.00% | 4.00% |
Measurement Input, Long-term Revenue Growth Rate | Elementum Holdings, L.P. | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Terminal revenue growth rate (as a percent) | 4.00% | 4.00% |
Measurement Input, Long-term Revenue Growth Rate | Other long-term investments | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Terminal revenue growth rate (as a percent) |  | 4.00% |
Terminal Multiple | Kudu's Participation Contracts | Standard Poors NR Rating |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Cash flow exit multiple, pretax | 10 | 10 |
Terminal Multiple | Kudu's Participation Contracts | Standard Poors NR Rating | Minimum |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Cash flow exit multiple | 7 | 7 |
Terminal Multiple | Kudu's Participation Contracts | Standard Poors NR Rating | Maximum |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Cash flow exit multiple | 13 | 12 |
Discounted Cash Flow Valuation Technique | Kudu's Participation Contracts | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, fair value | $ 669.5 | $ 400.6 |
Discounted Cash Flow Valuation Technique | PassportCard/DavidShield | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, fair value | 120.0 | 95.0 |
Discounted Cash Flow Valuation Technique | Elementum Holdings, L.P. | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, fair value | 45.0 | 55.1 |
Discounted Cash Flow Valuation Technique | Private debt investments | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, fair value | 9.4 | 17.1 |
Discounted Cash Flow Valuation Technique | Other long-term investments | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, fair value |  | $ 18.8 |
Probability Weighted Expected Return Method | Kudu's Participation Contracts | Standard Poors NR Rating | Level 3 |  |  |
Quantitative information for Level 3 Fair Value Measurements Assets |  |  |
Assets, fair value | $ 78.8 |  |

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