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.

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)(1)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

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Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

+ 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 (b)(3)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27290-111563

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The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Available for Sale Equity Securities Gross Unrealized Gains.

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Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI

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Securities In An Unrealized Loss Position Non-Investment Grade Fixed Maturity Securities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) position shares	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	$ 4,550,212		$ 5,160,888
Available For Sale Equity Securities Gross Unrealized Gains	404,192		453,298
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	73,546		99,268
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	4,498,967		5,129,763
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	69,292		94,583
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	0	$ 0
Aggregate fair value of securities in a continuous unrealized loss position	23,600		22,034
Available For Sale Equity Securities Gross Unrealized Gains	70,795		101,392
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	2,106		3,639
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	27,700
Aggregate fair value of securities in a continuous unrealized loss position	27,678		9,091
Available For Sale Equity Securities Gross Unrealized Gains	333,397		351,906
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	2,148		1,046
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	759,433		734,969
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	15,156		15,931
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	1,299,731		1,212,529
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	9,480		11,941
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	1,262,417		1,695,648
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	26,569		40,438
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	120,037		238,066
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	1,577		2,762
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Aggregate fair value of securities in a continuous unrealized loss position	929,025		1,100,392
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In AOCI	$ 14,290		$ 20,918
Noninvestment Grade Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities \| shares	1
Noninvestment Grade Investments at Loss Less than 5 Million [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	31
Aggregate fair value of securities in a continuous unrealized loss position	$ 106,289
Gross Unrealized Loss	$ 6,244
Noninvestment Grade Investments at Loss Less than 5 Million [Member] \| Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	9
Aggregate fair value of securities in a continuous unrealized loss position	$ 19,647
Gross Unrealized Loss	$ 924
Noninvestment Grade Investments at Loss Less than 5 Million [Member] \| Foreign Government Debt [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	11
Aggregate fair value of securities in a continuous unrealized loss position	$ 51,901
Gross Unrealized Loss	$ 681
Noninvestment Grade Investments at Loss Less than 5 Million [Member] \| Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities	4
Aggregate fair value of securities in a continuous unrealized loss position	$ 19,990
Gross Unrealized Loss	741
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Equity Securities Gross Unrealized Gains	$ 2,100
Noninvestment Grade Investments at Loss Less than 5 Million [Member] \| Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities \| position	6
Aggregate fair value of securities in a continuous unrealized loss position	$ 9,615
Gross Unrealized Loss	$ 173