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Investment Information - Investment in operating affiliates (Details) € / shares in Units, € in Thousands, $ in Thousands | 3 Months Ended | 6 Months Ended |  |
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Jun. 30, 2021 USD ($) | Jun. 30, 2020 USD ($) | Jun. 30, 2021 USD ($) | Jun. 30, 2021 EUR (€) | Jun. 30, 2020 USD ($) | Jun. 30, 2021 € / shares | Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Payments to Acquire Interest in Subsidiaries and Affiliates |  |  | $ 546,349 |  | $ 0 |  |
Investment in operating affiliates | $ 731,810 |  | 731,810 |  |  |  | $ 129,291
Income (loss) from operating affiliates | $ 24,476 | $ (3,173) | $ 99,933 |  | $ 5,343 |  |
Operating Affiliates |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Time lag for reporting |  |  | 3 months | 3 months |  |  |
Coface |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Percentage ownership | 29.50% |  | 29.50% |  |  |  |
Consideration paid per share | € / shares |  |  |  |  |  | € 9.95 |
Payments to Acquire Interest in Subsidiaries and Affiliates |  |  | $ 546,000 | € 453,000 |  |  |
Investment in operating affiliates | $ 601,900 |  | 601,900 |  |  |  |
Income (loss) from operating affiliates |  |  | 74,500 |  |  |  |
Purchase Of Affiliate, Deferred Gain | $ 36,000 |  | $ 36,000 |  |  |  |
Purchase Of Operating Affiliate, Deferred Gain, Period Of Recognition |  |  | 5 years | 5 years |  |  |

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