Investments (Summary Of Amortized Cost And Market Value Of Fixed Maturity Securities, By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	$ 5,060,968	$ 4,880,654
Fixed maturity securities - available for sale, at market value	5,326,118	5,107,028
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Due in one year or less, Amortized Cost	351,241	224,406
Fixed maturity securities - available for sale, Due after one year through five years, Amortized Cost	2,272,775	2,055,299
Fixed maturity securities - available for sale, Due after five years through ten years, Amortized Cost	977,030	955,253
Fixed maturity securities - available for sale, Due after ten years, Amortized Cost	803,926	1,006,307
Fixed maturity securities - available for sale, Due in one year or less, Market Value	349,065	223,507
Fixed maturity securities - available for sale, Due after one year through five years, Market Value	2,360,911	2,129,437
Fixed maturity securities - available for sale, Due after five years through ten years, Market Value	1,040,976	1,009,893
Fixed maturity securities - available for sale, Due after ten years, Market Value	893,588	1,083,532
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	48,695	44,351
Fixed maturity securities - available for sale, at market value	50,923	45,103
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	45,345	41,953
Fixed maturity securities - available for sale, at market value	53,007	47,874
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	559,808	528,946
Fixed maturity securities - available for sale, at market value	575,168	543,393
Non-agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	2,148	24,139
Fixed maturity securities - available for sale, at market value	$ 2,480	$ 24,289

Amount of debt securities categorized neither as held-to-maturity nor trading, held at market value.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at fair value maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing after the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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