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Investments Realized and Unrealized Gains (Losses) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Gain (Loss) on Securities [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gross gains on sales |  |  |  |  |  |  |  |  | $ 18,893 | $ 31,910 | $ 28,672
Gross losses on sales |  |  |  |  |  |  |  |  | (9,745) | (5,195) | (47,647)
Net realized investment gains (losses) on disposals |  |  |  |  |  |  |  |  | 9,148 | 26,715 | (18,975)
Net unrealized losses on equity securities |  |  |  |  |  |  |  |  | 7,939 | (8,649) | (29,369)
Losses on securities for which we have the intent to sell |  |  |  |  |  |  |  |  | (16,266) |  |
OTTI Losses Gross |  |  |  |  |  |  |  |  |  | (3,644) | (6,579)
Net realized and unrealized investment (losses) gain | $ 20,079 | $ 7,721 | $ 12,649 | $ (44,666) | $ (873) | $ (2,183) | $ 4,027 | $ 13,451 | (4,217) | $ 14,422 | $ (54,923)
Available-for-sale Securities [Member] |  |  |  |  |  |  |  |  |  |  |
Credit loss expense on investment portfolio |  |  |  |  |  |  |  |  | (5,042) |  |
Held-to-maturity Securities [Member] |  |  |  |  |  |  |  |  |  |  |
Credit loss expense on investment portfolio |  |  |  |  |  |  |  |  | $ 4 |  |

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- Definition Amount of unrealized and realized gain (loss) on investment in debt and equity securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(9)(a)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(7)(c)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details
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