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Investments (Number of Securities in an Unrealized Unrecognized Loss Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Percentage Decline in Fair Value Percentage of Amortized Cost	2.00%	1.00%
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	$ 200	$ 100
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		878,126
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(4,961)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		35,686
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		(397)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value		913,812
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(5,358)
AFS Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	2,142,433	869,566
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(36,948)	(4,664)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	275,174	35,686
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(8,119)	(397)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	2,417,607	905,252
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(45,067)	(5,061)
Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		8,560
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(297)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value		8,560
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(297)
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	6,693	23,516
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(174)	(233)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	23,163	250
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(418)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	29,856	23,766
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(592)	(233)
Foreign Government [Member] | AFS Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	12,208	1,481
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(93)	(11)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,482	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(14)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	13,690	1,481
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(107)	(11)
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	196,798	107,514
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,074)	(422)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	42,821	14,139
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(557)	(160)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	239,619	121,653
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2,631)	(582)
Corporate Securities [Member] | AFS Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,041,952	238,326
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(23,649)	(1,744)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	78,953	3,228
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4,316)	(18)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	1,120,905	241,554
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(27,965)	(1,762)
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	516,106	74,977
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(6,750)	(196)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	16,800	1,655
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(193)	(6)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	532,906	76,632
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(6,943)	(202)
Commercial Mortgage Backed Securities [Member] | AFS Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	229,338	154,267
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,548)	(773)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	66,294	5,214
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,200)	(68)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	295,632	159,481
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(3,748)	(841)
Residential Mortgage Backed Securities [Member] | AFS Fixed Maturity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	139,338	269,485
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,660)	(1,285)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	45,661	11,200
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1,421)	(145)
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value	184,999	280,685
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (3,081)	(1,430)
Common Stock [Member] | Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		4,727
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(226)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value		4,727
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		(226)
Nonredeemable Preferred Stock [Member] | Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		3,833
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(71)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Total Fair Value		3,833
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ (71)

X

- Definition

This item represents the percentage decline in fair value of fixed maturity securities compared to amortized cost that have been in a loss position for more than twelve months. This impairment has been determined to be temporary.

+ References

No definition available.

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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.

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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

No definition available.

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- Definition

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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- Definition

This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

+ References

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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 less than twelve months.

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- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

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