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Investments (Fair Value Below Amortized Cost of Gross Unrealized Losses for Fixed Maturity and Equity Securities) (Details) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2017 | Dec. 31, 2016
Gross unrealized losses with number of securities [Line Items] |  |
Gross Unrealized Losses | $ 179,081 | $ 374,857
% of Total | 100.00% | 100.00%
Less than 20% |  |
Gross unrealized losses with number of securities [Line Items] |  |
Gross Unrealized Losses | $ 150,762 | $ 337,831
% of Total | 84.20% | 90.10%
20% or more for less than six months |  |
Gross unrealized losses with number of securities [Line Items] |  |
Gross Unrealized Losses | $ 7,593 | $ 19,438
% of Total | 4.20% | 5.20%
20% or more for six months or greater |  |
Gross unrealized losses with number of securities [Line Items] |  |
Gross Unrealized Losses | $ 20,726 | $ 17,588
% of Total | 11.60% | 4.70%

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- Definition Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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