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Investments (Number of Securities in an Unrealized Unrecognized Loss Position) (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Percentage Decline in Fair Value Percentage of Amortized Cost | 1.00% | 1.00%
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss | $ 100 | $ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 878,126 | 1,358,111
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (4,961) | (15,651)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 35,686 | 15,626
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (397) | (406)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 913,812 | 1,373,737
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (5,358) | (16,057)
AFS Fixed Maturity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 869,566 | 1,340,672
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (4,664) | (14,991)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 35,686 | 15,626
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (397) | (406)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 905,252 | 1,356,298
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (5,061) | (15,397)
Equity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 8,560 | 17,439
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (297) | (660)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 8,560 | 17,439
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (297) | (660)
U.S. Government and Government Agencies [Member] | AFS Fixed Maturity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 23,516 | 6,419
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (233) | (36)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 250 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 23,766 | 6,419
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (233) | (36)
Foreign Government [Member] | AFS Fixed Maturity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 1,481 | 13,075
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (11) | (16)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 1,481 | 13,075
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (11) | (16)
Obligations of States and Political Subdivisions [Member] | AFS Fixed Maturity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 107,514 | 306,509
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (422) | (5,304)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 14,139 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (160) | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 121,653 | 306,509
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (582) | (5,304)
Corporate Securities [Member] | AFS Fixed Maturity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 238,326 | 462,902
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (1,744) | (5,771)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 3,228 | 4,913
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (18) | (89)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 241,554 | 467,815
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (1,762) | (5,860)
Collateralized Loan Obligations and Other Asset-Backed Securities [Member] | AFS Fixed Maturity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 74,977 | 189,795
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (196) | (354)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 1,655 | 319
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (6) | (1)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 76,632 | 190,114
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (202) | (355)
Commercial Mortgage Backed Securities [Member] | AFS Fixed Maturity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 154,267 | 82,492
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (773) | (1,021)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 5,214 | 1,645
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (68) | (7)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 159,481 | 84,137
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (841) | (1,028)
Residential Mortgage Backed Securities [Member] | AFS Fixed Maturity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 269,485 | 279,480
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (1,285) | (2,489)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 11,200 | 8,749
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | (145) | (309)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 280,685 | 288,229
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (1,430) | (2,798)
Common Stock [Member] | Equity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 4,727 | 11,271
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (226) | (305)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 4,727 | 11,271
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | (226) | (305)
Nonredeemable Preferred Stock [Member] | Equity Securities [Member] |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 3,833 | 6,168
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (71) | (355)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | 0 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value | 3,833 | 6,168
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | $ (71) | $ (355)

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- Definition This item represents the sum of (i) the excess of amortized cost over fair value for available-for-sale securities that are in a loss position and (ii) the market fluctuations on held-to-maturity securities from the later of (a) the date a security is designated as held-to-maturity; or (b) the date that an other-than-temporary impairment charge is recognized on a held-to-maturity security for securities that are in an unrecognized loss position. + References No definition available. + Details
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- Definition Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563 + Details
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