Investments (Summary Of Amortized Cost And Market Value Of Fixed Maturity Securities, By Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	$ 5,380,387	$ 5,289,619
Fixed maturity securities - available for sale, at market value	5,611,463	5,531,410
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	303,216	329,474
Fixed maturity securities - available for sale, Due after one year through five years, Amortized Cost	2,537,939	2,380,093
Fixed maturity securities - available for sale, Due after five years through ten years, Amortized Cost	959,270	1,008,653
Fixed maturity securities - available for sale, Due after ten years, Amortized Cost	729,329	807,515
Fixed maturity securities - available for sale, Due in one year or less, Market Value	303,754	330,149
Fixed maturity securities - available for sale, Due after one year through five years, Market Value	2,631,420	2,462,430
Fixed maturity securities - available for sale, Due after five years through ten years, Market Value	1,006,214	1,064,579
Fixed maturity securities - available for sale, Due after ten years, Market Value	802,600	889,090
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	46,837	44,070
Fixed maturity securities - available for sale, at market value	49,127	46,487
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	45,094	45,157
Fixed maturity securities - available for sale, at market value	52,259	52,624
Agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	757,378	672,724
Fixed maturity securities - available for sale, at market value	764,616	683,722
Non-agency Residential [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturity securities - available for sale, Amortized Cost	1,324	1,933
Fixed maturity securities - available for sale, at market value	$ 1,473	$ 2,329

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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