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Investment Information - Limited partnership interests (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
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Schedule of Equity Method Investments [Line Items] |  |  |
Maximum Exposure to Loss |  | $ 2,064,111 | $ 1,848,679
Aggregate unfunded commitments |  | 1,910,000 | 1,690,000
Equity method investments |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Maximum Exposure to Loss | [1] | 1,883,702 | 1,660,396
Aggregate unfunded commitments |  | 1,590,000 | 1,360,000
Fair value option |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |
Maximum Exposure to Loss | [2] | 180,409 | 188,283
Aggregate unfunded commitments |  | $ 36,700 | $ 41,700
[1] | Aggregate unfunded commitments were $1.59 billion at September 30, 2020, compared to $1.36 billion at December 31, 2019.
[2] | Aggregate unfunded commitments were $36.7 million at September 30, 2020, compared to $41.7 million at December 31, 2019.

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