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Investments (Net Investment Income) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | $ 68,185 | $ 55,826 | $ 158,596 | $ 164,949
Fixed Income Securities [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 51,285 | 50,749 | 152,617 | 150,689
Commercial Mortgage Loans [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 245 | 0 | 463 | 0
Equity Securities [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 1,948 | 1,885 | 5,523 | 5,265
Short-Term Investments [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 244 | 1,410 | 1,830 | 5,213
Other Investments [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | 18,671 | 5,267 | 9,167 | 13,421
Investment Expenses [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | (4,208) | (3,485) | (11,004) | (9,639)
Alternative Investments [Member] |  |  |  |
Net Investment Income [Line Items] |  |  |  |
Net investment income earned | $ 18,700 | $ 5,200 | $ 8,900 | $ 13,000

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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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