Investments (Summary Of Unrealized Appreciation (Depreciation) Of Available For Sale, Fixed Maturity And Equity Security Investments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 12,708,891	$ 12,391,164
Unrealized Appreciation	427,746	410,338
Unrealized Depreciation	(117,461)	(164,595)
Market Value	13,019,176	12,636,907
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	161,235	160,013
Unrealized Appreciation	2,755	2,690
Unrealized Depreciation	(1,711)	(1,678)
Market Value	162,279	161,025
Obligations Of U.S. States And Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	927,315	970,735
Unrealized Appreciation	43,571	40,815
Unrealized Depreciation	(4,562)	(9,022)
Market Value	966,324	1,002,528
Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,311,095	3,950,887
Unrealized Appreciation	162,455	155,619
Unrealized Depreciation	(19,196)	(27,090)
Market Value	4,454,354	4,079,416
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	181,005	169,980
Unrealized Appreciation	3,273	3,485
Unrealized Depreciation	(214)	(422)
Market Value	184,064	173,043
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	234,356	254,765
Unrealized Appreciation	16,000	16,683
Unrealized Depreciation	(1,022)	(1,007)
Market Value	249,334	270,441
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,209,374	2,294,719
Unrealized Appreciation	35,761	34,509
Unrealized Depreciation	(30,791)	(50,175)
Market Value	2,214,344	2,279,053
Non-Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,302	4,816
Unrealized Appreciation	287	229
Unrealized Depreciation	(184)	(226)
Market Value	4,405	4,819
Foreign Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,700,019	1,740,337
Unrealized Appreciation	72,058	69,779
Unrealized Depreciation	(23,806)	(29,347)
Market Value	1,748,271	1,780,769
Foreign Corporate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,980,190	2,844,912
Unrealized Appreciation	91,586	86,529
Unrealized Depreciation	(35,975)	(45,628)
Market Value	3,035,801	2,885,813
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	156,000	148,342
Unrealized Appreciation	4,828	4,336
Unrealized Depreciation	(7,006)	(8,597)
Market Value	$ 153,822	$ 144,081

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

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+ Details

- Definition

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+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details