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Investments (Other Investment Portfolio by Strategy and the Remaining Commitment Amount Associated With Each Strategy) (Details) - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Carrying Value | $ 178,938 | $ 132,268
Other Investment Portfolio [Member] |  |
Carrying Value | 178,938 | 132,268
Remaining Commitment | 202,270 | 220,999
Maximum Exposure to Loss | 381,208 | 353,267
Alternative Investments [Member] |  |
Carrying Value | 153,896 | 115,373
Remaining Commitment | 202,270 | 220,999
Maximum Exposure to Loss | 356,166 | 336,372
Private Equity [Member] | Alternative Investments [Member] |  |
Carrying Value | 84,352 | 52,251
Remaining Commitment | 93,688 | 99,026
Maximum Exposure to Loss | 178,040 | 151,277
Private Credit Funds [Member] | Alternative Investments [Member] |  |
Carrying Value | 41,682 | 37,743
Remaining Commitment | 81,453 | 94,959
Maximum Exposure to Loss | 123,135 | 132,702
Real Assets [Member] | Alternative Investments [Member] |  |
Carrying Value | 27,862 | 25,379
Remaining Commitment | 27,129 | 27,014
Maximum Exposure to Loss | 54,991 | 52,393
Other Securities [Member] |  |
Carrying Value | 25,042 | 16,895
Remaining Commitment | 0 | 0
Maximum Exposure to Loss | $ 25,042 | $ 16,895

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