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Investments (Fair Value and Gross Pre-Tax Net Unrealized Unrecognized Loss of Securities By Length of Time) (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Dec. 31, 2015
AFS Fair Value, Less than 12 months		$ 303,470	$ 1,449,183
AFS Unrealized Losses, Less than 12 months	[1]	(2,726)	(19,953)
AFS Fair Value, 12 months or longer		79,305	141,580
AFS Unrealized Losses, 12 months or longer	[1]	(601)	(4,900)
AFS Fixed Income Securities [Member]
AFS Fair Value, Less than 12 months		290,942	1,416,504
AFS Unrealized Losses, Less than 12 months	[1]	(1,637)	(17,915)
AFS Fair Value, 12 months or longer		79,305	141,580
AFS Unrealized Losses, 12 months or longer	[1]	(601)	(4,900)
AFS Fixed Income Securities [Member] | U.S. Government and Government Agencies [Member]
AFS Fair Value, Less than 12 months			16,006
AFS Unrealized Losses, Less than 12 months	[1]		(87)
AFS Fair Value, 12 months or longer			396
AFS Unrealized Losses, 12 months or longer	[1]		(4)
AFS Fixed Income Securities [Member] | Foreign Government [Member]
AFS Fair Value, Less than 12 months			1,067
AFS Unrealized Losses, Less than 12 months	[1]		(2)
AFS Fair Value, 12 months or longer			0
AFS Unrealized Losses, 12 months or longer	[1]		0
AFS Fixed Income Securities [Member] | Obligations of States and Political Subdivisions [Member]
AFS Fair Value, Less than 12 months		74,989	28,617
AFS Unrealized Losses, Less than 12 months	[1]	(333)	(160)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	0	0
AFS Fixed Income Securities [Member] | Corporate Securities [Member]
AFS Fair Value, Less than 12 months		155,880	761,479
AFS Unrealized Losses, Less than 12 months	[1]	(1,139)	(12,671)
AFS Fair Value, 12 months or longer		30,469	50,382
AFS Unrealized Losses, 12 months or longer	[1]	(288)	(2,850)
AFS Fixed Income Securities [Member] | Asset-Backed Securities [Member]
AFS Fair Value, Less than 12 months		21,766	197,477
AFS Unrealized Losses, Less than 12 months	[1]	(66)	(807)
AFS Fair Value, 12 months or longer		2,450	12,022
AFS Unrealized Losses, 12 months or longer	[1]	(3)	(111)
AFS Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
AFS Fair Value, Less than 12 months		24,633	146,944
AFS Unrealized Losses, Less than 12 months	[1]	(59)	(2,196)
AFS Fair Value, 12 months or longer		8,709	15,385
AFS Unrealized Losses, 12 months or longer	[1]	(34)	(214)
AFS Fixed Income Securities [Member] | Residential Mortgage Backed Securities [Member]
AFS Fair Value, Less than 12 months		13,674	264,914
AFS Unrealized Losses, Less than 12 months	[1]	(40)	(1,992)
AFS Fair Value, 12 months or longer		37,677	63,395
AFS Unrealized Losses, 12 months or longer	[1]	(276)	(1,721)
Equity Securities [Member]
AFS Fair Value, Less than 12 months		12,528	32,679
AFS Unrealized Losses, Less than 12 months	[1]	(1,089)	(2,038)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	0	0
Equity Securities [Member] | Common Stock [Member]
AFS Fair Value, Less than 12 months		12,528	31,148
AFS Unrealized Losses, Less than 12 months	[1]	(1,089)	(1,998)
AFS Fair Value, 12 months or longer		0	0
AFS Unrealized Losses, 12 months or longer	[1]	$ 0	0
Equity Securities [Member] | Preferred Stock [Member]
AFS Fair Value, Less than 12 months			1,531
AFS Unrealized Losses, Less than 12 months	[1]		(40)
AFS Fair Value, 12 months or longer			0
AFS Unrealized Losses, 12 months or longer	[1]		$ 0
[1] Gross unrealized losses include non-OTTI unrealized amounts and OTTI losses recognized in AOCI.

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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=73527792&loc=d3e27290-111563

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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+ References

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