Investments (Summary Of Unrealized Appreciation (Depreciation) Of Available For Sale, Fixed Maturity And Equity Security Investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 5,617,412	$ 5,335,472
Unrealized Appreciation	191,359	121,337
Unrealized Depreciation	(40,022)	(100,332)
Market Value	5,768,749	5,356,477
OTTI in AOCI	6,574	(69)
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	383,388	329,281
Unrealized Appreciation	8,705	2,422
Unrealized Depreciation	(149)	(718)
Market Value	391,944	330,985
Obligations of U.S. States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	701,171	669,945
Unrealized Appreciation	49,219	34,020
Unrealized Depreciation	(478)	(890)
Market Value	749,912	703,075
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,032,340	2,011,997
Unrealized Appreciation	54,062	27,286
Unrealized Depreciation	(20,239)	(70,725)
Market Value	2,066,163	1,968,558
OTTI in AOCI	4,451	(86)
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	167,478	145,755
Unrealized Appreciation	1,592	290
Unrealized Depreciation	(157)	(1,063)
Market Value	168,913	144,982
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	73,543	61,527
Unrealized Appreciation	1,623	1,430
Unrealized Depreciation	(65)	(511)
Market Value	75,101	62,446
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	756,403	714,907
Unrealized Appreciation	11,867	3,994
Unrealized Depreciation	(574)	(6,603)
Market Value	767,696	712,298
Non-agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	103	126
Unrealized Appreciation	17	24
Market Value	120	150
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	512,414	447,244
Unrealized Appreciation	28,986	24,255
Unrealized Depreciation	(7,997)	(8,425)
Market Value	533,403	463,074
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	990,572	954,690
Unrealized Appreciation	35,288	27,616
Unrealized Depreciation	(10,363)	(11,397)
Market Value	1,015,497	970,909
OTTI in AOCI	$ 2,123	$ 17

Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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