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Fair Value Measurement (Quantitative Information Regarding Level 3 Valuations) (Details) $ in Thousands | Sep. 30, 2021 USD ($) | Dec. 31, 2020 USD ($)
--- | --- | ---
Assets: |  |
Estimated Fair Value | $ 3,904,136 | $ 2,457,531
Level 3 |  |
Assets: |  |
Equity securities | 2,569 | 0
Other liabilities | $ 24,000 | 0
Level 3 | Stochastic Model/Discounted Cash Flows | Minimum |  |
Assets: |  |
Other Liabilities, Measurement Input | 0.00% |
Level 3 | Stochastic Model/Discounted Cash Flows | Maximum |  |
Assets: |  |
Other Liabilities, Measurement Input | 10.00% |
Level 3 | Stochastic Model/Discounted Cash Flows | Weighted Average |  |
Assets: |  |
Other Liabilities, Measurement Input | 8.00% |
Level 3 | Comparability Adjustment | Minimum |  |
Assets: |  |
Equity securities measured at fair value | 0 |
Level 3 | Comparability Adjustment | Maximum |  |
Assets: |  |
Equity securities measured at fair value | 0.10 |
Level 3 | Comparability Adjustment | Weighted Average |  |
Assets: |  |
Equity securities measured at fair value | 0.05 |
Corporate debt, limited observable inputs | Level 3 |  |
Assets: |  |
Estimated Fair Value | $ 19,712 | 3,265
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Market Comparable Securities | Minimum |  |
Assets: |  |
Assets measured at fair value | 0 |
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Market Comparable Securities | Maximum |  |
Assets: |  |
Assets measured at fair value | 0.05 |
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Market Comparable Securities | Weighted Average |  |
Assets: |  |
Assets measured at fair value | 0.025 |
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Discounted Cash Flows | Minimum |  |
Assets: |  |
Assets measured at fair value | 0 |
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Discounted Cash Flows | Maximum |  |
Assets: |  |
Assets measured at fair value | 0.05 |
Corporate debt, limited observable inputs | Level 3 | Comparability Adjustment | Discounted Cash Flows | Weighted Average |  |
Assets: |  |
Assets measured at fair value | 0.025 |
Residential mortgage-backed securities | Level 3 |  |
Assets: |  |
Estimated Fair Value | $ 4,235 | 2,032
Residential mortgage-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Minimum |  |
Assets: |  |
Assets measured at fair value | 0 |
Residential mortgage-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Maximum |  |
Assets: |  |
Assets measured at fair value | 0.05 |
Residential mortgage-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Weighted Average |  |
Assets: |  |
Assets measured at fair value | 0.025 |
Residential mortgage-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Minimum |  |
Assets: |  |
Assets measured at fair value | 0 |
Residential mortgage-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Maximum |  |
Assets: |  |
Assets measured at fair value | 0.05 |
Residential mortgage-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Weighted Average |  |
Assets: |  |
Assets measured at fair value | 0.025 |
Other asset-backed securities | Level 3 |  |
Assets: |  |
Estimated Fair Value | $ 11,007 | $ 6,661
Other asset-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Minimum |  |
Assets: |  |
Assets measured at fair value | 0 |
Other asset-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Maximum |  |
Assets: |  |
Assets measured at fair value | 0.05 |
Other asset-backed securities | Level 3 | Comparability Adjustment | Market Comparable Securities | Weighted Average |  |
Assets: |  |
Assets measured at fair value | 0.025 |
Other asset-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Minimum |  |
Assets: |  |
Assets measured at fair value | 0 |
Other asset-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Maximum |  |
Assets: |  |
Assets measured at fair value | 0.05 |
Other asset-backed securities | Level 3 | Comparability Adjustment | Discounted Cash Flows | Weighted Average |  |
Assets: |  |
Assets measured at fair value | 0.025 |

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