Investments (Summary Of Amortized Cost And Market Value Of Fixed Maturity Securities, By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	$ 4,991,177	$ 4,880,654
Fixed maturity securities - available for sale, at market value	5,228,179	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	367,937	224,406
Fixed maturity securities - available for sale, Due after one year through five years, Amortized Cost	2,197,306	2,055,299
Fixed maturity securities - available for sale, Due after five years through ten years, Amortized Cost	891,434	955,253
Fixed maturity securities - available for sale, Due after ten years, Amortized Cost	895,196	1,006,307
Fixed maturity securities - available for sale, Due in one year or less, Market Value	366,220	223,507
Fixed maturity securities - available for sale, Due after one year through five years, Market Value	2,274,862	2,129,437
Fixed maturity securities - available for sale, Due after five years through ten years, Market Value	944,813	1,009,893
Fixed maturity securities - available for sale, Due after ten years, Market Value	982,330	1,083,532
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	48,367	44,351
Fixed maturity securities - available for sale, at market value	49,723	45,103
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	46,126	41,953
Fixed maturity securities - available for sale, at market value	52,770	47,874
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	542,268	528,946
Fixed maturity securities - available for sale, at market value	554,590	543,393
Non-agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	2,543	24,139
Fixed maturity securities - available for sale, at market value	$ 2,871	$ 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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