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Investments (Other Investment Portfolio by Strategy and the Remaining Commitment Amount and Maximum Exposure to Loss Associated With Each Strategy) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Net investment income earned |  | $ 93,032 | $ 68,185 | $ 246,479 | $ 158,596 |
Carrying Value |  | 392,788 |  | 392,788 |  | $ 266,322
Alternative Investments [Member] |  |  |  |  |  |
Net investment income earned |  | 42,800 | $ 18,700 | 92,900 | $ 8,900 |
Other Securities [Member] |  |  |  |  |  |
Carrying Value |  | 50,296 |  | 50,296 |  | 35,370
Remaining Commitment |  | 0 |  | 0 |  | 0
Maximum Exposure to Loss | [1] | 50,296 |  | 50,296 |  | 35,370
Alternative Investments [Member] |  |  |  |  |  |
Carrying Value |  | 342,492 |  | 342,492 |  | 230,952
Remaining Commitment |  | 219,249 |  | 219,249 |  | 215,728
Maximum Exposure to Loss | [1] | 561,741 |  | 561,741 |  | 446,680
Alternative Investments [Member] | Private Equity Funds [Member] |  |  |  |  |  |
Carrying Value |  | 257,160 |  | 257,160 |  | 157,276
Remaining Commitment |  | 103,792 |  | 103,792 |  | 100,905
Maximum Exposure to Loss | [1] | 360,952 |  | 360,952 |  | 258,181
Alternative Investments [Member] | Private Credit Funds [Member] |  |  |  |  |  |
Carrying Value |  | 62,462 |  | 62,462 |  | 54,017
Remaining Commitment |  | 91,991 |  | 91,991 |  | 98,330
Maximum Exposure to Loss | [1] | 154,453 |  | 154,453 |  | 152,347
Alternative Investments [Member] | Real Assets [Member] |  |  |  |  |  |
Carrying Value |  | 22,870 |  | 22,870 |  | 19,659
Remaining Commitment |  | 23,466 |  | 23,466 |  | 16,493
Maximum Exposure to Loss | [1] | 46,336 |  | 46,336 |  | 36,152
Other Investments [Member] |  |  |  |  |  |
Carrying Value |  | 392,788 |  | 392,788 |  | 266,322
Remaining Commitment |  | 219,249 |  | 219,249 |  | 215,728
Maximum Exposure to Loss | [1] | $ 612,037 |  | $ 612,037 |  | $ 482,050
[1] | The maximum exposure to loss includes both the carry value of these investments and the related remaining commitments. In addition, tax credits that have been previously recognized in Other securities are subject to the risk of recapture, which we do not consider significant.

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- Definition This item represents contractual obligations to invest additional amounts on our other investment portfolio. These additional investments may or may not be required. + References No definition available. + Details
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- Definition Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(2)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
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- Definition Amount of investments classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1(f,g)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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