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Investments (Net Realized Gains (Losses) on Disposals) (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items] |  |  |  |
HTM fixed income securities Gains | $ 0 | $ 0 | $ 2 | $ 44
HTM fixed income securities Losses | 0 | 0 | 0 | (1)
Equity securities Gains | 10,584 |  | 20,209 |
Equity securities Losses | (1,919) |  | (2,249) |
Short-term investments Gains | 3 | 0 | 6 | 2
Short-term investments Losses | (1) | 0 | (5) | (2)
Other investments Gains | 0 | 0 | 0 | 480
Other investments Losses | (5) | 0 | (5) | (19)
Net realized investment (losses) gains on disposals | (751) | 6,871 | 4,034 | 12,252
Sale of fixed income securities, available-for-sale | 444,400 | 94,900 | 1,382,677 | 811,991
Sale of equity securities | 36,100 |  | 79,676 |
Sale of equity securities, available-for-sale |  | 12,700 |  | 19,007
Fixed Maturities [Member] |  |  |  |
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items] |  |  |  |
AFS securities Gains | 462 | 2,070 | 5,056 | 8,337
AFS securities Losses | (9,875) | (74) | (18,980) | (1,814)
Equity Securities [Member] |  |  |  |
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items] |  |  |  |
AFS securities Gains |  | 4,875 |  | 5,225
AFS securities Losses |  | 0 |  | 0
Net realized investment (losses) gains on disposals | $ 8,665 | $ 4,875 | $ 17,960 | $ 5,225

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