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Schedule of Total Investment Return (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Investments Debt And Equity Securities [Abstract] |  |  |  |  |
Net investment income |  | $ 11,746 | $ 11,348 | $ 19,516 | $ 32,393
Net realized investment gains (losses) |  | 7,323 | (2,690) | (22,332) | 11,290
Change in unrealized holding gains and losses |  | 32 | 10,021 | 22,190 | 53,457
Net realized and unrealized investment returns |  | 7,355 | 7,331 | (142) | 64,747
Total investment return |  | $ 19,101 | $ 18,679 | $ 19,374 | $ 97,140
Total investment return % | [1] | 1.20% | 1.20% | 1.30% | 6.20%
Average investment portfolio | [2] | $ 1,541,227 | $ 1,585,165 | $ 1,528,005 | $ 1,562,177
[1] | Not annualized.
[2] | Average of total cash and invested assets, net of receivable/payable for securities purchased and sold, as of the beginning and end of the period.

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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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