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Investments (Net Realized Gains (Losses) on Disposals) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items] |  |  |  |
HTM fixed income securities Gains | $ 0 | $ 44 | $ 2 | $ 44
HTM fixed income securities Losses | 0 | 0 | 0 | (1)
Equity securities Gains | 1,226 |  | 9,625 |
Equity securities Losses | 0 |  | (330) |
Short-term investments Gains | 2 | 0 | 3 | 2
Short-term investments Losses | 0 | 0 | (4) | (2)
Other investments Gains | 0 | 0 | 0 | 480
Other investments Losses | 0 | (5) | 0 | (19)
Net realized investment gains on disposals | 54 | 2,951 | 4,785 | 5,381
Sale of fixed income securities, available-for-sale | 262,900 | 122,300 | 938,276 | 717,072
Sale of equity securities | 2,900 |  | 43,590 |
Sale of equity securities, available-for-sale |  | 800 |  | 6,289
Fixed Maturities [Member] |  |  |  |
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items] |  |  |  |
AFS fixed income securities Gains | 1,971 | 2,715 | 4,594 | 6,267
AFS fixed income securities Losses | (3,145) | (153) | (9,105) | (1,740)
Equity Securities [Member] |  |  |  |
Schedule of Realized Gains (Losses) on Disposals Excluding OTTI [Line Items] |  |  |  |
AFS fixed income securities Gains |  | 350 |  | 350
AFS fixed income securities Losses |  | 0 |  | 0
Net realized investment gains on disposals | $ 1,226 | $ 350 | $ 9,295 | $ 350

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