Investments (Summary Of Unrealized Appreciation (Depreciation) Of Available For Sale, Fixed Maturity And Equity Security Investments) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fixed Maturity Securities [Member]
Investment [Line Items]
Amortized Cost	$ 5,060,968	$ 4,880,654
Unrealized Appreciation	287,297	261,842
Unrealized Depreciation	(22,147)	(35,468)
Market Value	5,326,118	5,107,028
U.S. Treasury Securities And Obligations Of U.S. Government Agencies And Corporations [Member]
Investment [Line Items]
Amortized Cost	77,754	77,351
Unrealized Appreciation	1,658	2,475
Unrealized Depreciation	(817)	(287)
Market Value	78,595	79,539
US States and Political Subdivisions Debt Securities [Member]
Investment [Line Items]
Amortized Cost	1,275,967	1,558,615
Unrealized Appreciation	90,415	102,815
Unrealized Depreciation	(53)	(525)
Market Value	1,366,329	1,660,905
Corporate Debt Securities [Member]
Investment [Line Items]
Amortized Cost	1,342,335	1,200,941
Unrealized Appreciation	65,091	45,070
Unrealized Depreciation	(6,198)	(17,776)
Market Value	1,401,228	1,228,235
Asset-backed Securities [Member]
Investment [Line Items]
Amortized Cost	48,695	44,351
Unrealized Appreciation	2,228	758
Unrealized Depreciation		(6)
Market Value	50,923	45,103
Commercial Mortgage Backed Securities [Member]
Investment [Line Items]
Amortized Cost	45,345	41,953
Unrealized Appreciation	8,066	7,187
Unrealized Depreciation	(404)	(1,266)
Market Value	53,007	47,874
Agency Residential [Member]
Investment [Line Items]
Amortized Cost	559,808	528,946
Unrealized Appreciation	15,901	16,209
Unrealized Depreciation	(541)	(1,762)
Market Value	575,168	543,393
Non-agency Residential [Member]
Investment [Line Items]
Amortized Cost	2,148	24,139
Unrealized Appreciation	357	470
Unrealized Depreciation	(25)	(320)
Market Value	2,480	24,289
Foreign Government Debt Securities [Member]
Investment [Line Items]
Amortized Cost	759,964	733,814
Unrealized Appreciation	56,900	57,437
Unrealized Depreciation	(4,176)	(2,602)
Market Value	812,688	788,649
Foreign Corporate Debt Securities [Member]
Investment [Line Items]
Amortized Cost	948,952	670,544
Unrealized Appreciation	46,681	29,421
Unrealized Depreciation	(9,933)	(10,924)
Market Value	985,700	689,041
Equity Securities [Member]
Investment [Line Items]
Amortized Cost	15	15
Unrealized Depreciation	(2)	(5)
Market Value	$ 13	$ 10

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 FASB Staff Position (FSP)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

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

-Publisher FASB

-Name Accounting Standards Codification

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

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

-Publisher FASB

-Name Accounting Standards Codification

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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

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Reference 9: 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 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

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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