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Investments (Net Investment Income) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | $ 97,696 | $ 70,222 | $ 189,202 | $ 142,824
Fixed Income Securities [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 83,916 | 62,144 | 164,003 | 116,069
Commercial Mortgage Loans [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 2,199 | 1,192 | 4,164 | 2,162
Equity Securities [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 2,236 | 2,639 | 3,441 | 5,057
Short-Term Investments [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 2,892 | 407 | 7,542 | 508
Alternative Investments [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 11,396 | 9,274 | 19,164 | 28,402
Other Investments [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 188 | (214) | 231 | (37)
Investment expenses [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | $ (5,131) | $ (5,220) | $ (9,343) | $ (9,337)

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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 https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
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