Investments (Tables)

12 Months Ended

Dec. 31, 2011

Investments [Abstract]

Available For Sale, Fixed Maturity And Equity Security Investments

	At December 31, 2011
	Amortized		Unrealized		Unrealized			Market
(Dollars in thousands)	Cost		Appreciation		Depreciation			Value
Fixed maturity securities
U.S. Treasury securities and obligations of
U.S. government agencies and corporations	$	284,514	$	16,407	$	(287	)	$	300,634
Obligations of U.S. states and political subdivisions		1,558,615		102,815		(525	)		1,660,905
Corporate securities		3,495,761		197,914		(27,054	)		3,666,621
Asset-backed securities		186,936		7,020		(550	)		193,406
Mortgage-backed securities
Commercial		310,387		20,942		(9,902	)		321,427
Agency residential		2,198,937		86,722		(3,066	)		2,282,593
Non-agency residential		53,365		499		(775	)		53,089
Foreign government securities		1,555,707		120,900		(8,389	)		1,668,218
Foreign corporate securities		2,086,951		91,869		(32,189	)		2,146,631
Total fixed maturity securities	$	11,731,173	$	645,088	$	(82,737	)	$	12,293,524
Equity securities	$	463,620	$	4,060	$	(18,750	)	$	448,930

	At December 31, 2010
	Amortized		Unrealized		Unrealized			Market
(Dollars in thousands)	Cost		Appreciation		Depreciation			Value
Fixed maturity securities
U.S. Treasury securities and obligations of
U.S. government agencies and corporations	$	394,690	$	12,772	$	(5,655	)	$	401,807
Obligations of U.S. states and political subdivisions		2,809,514		116,920		(24,929	)		2,901,505
Corporate securities		2,916,977		168,687		(16,518	)		3,069,146
Asset-backed securities		210,717		7,799		(215	)		218,301
Mortgage-backed securities
Commercial		324,922		17,751		(5,454	)		337,219
Agency residential		2,018,384		76,367		(1,469	)		2,093,282
Non-agency residential		76,259		1,205		(1,723	)		75,741
Foreign government securities		1,584,355		79,661		(25,668	)		1,638,348
Foreign corporate securities		1,675,518		71,268		(31,666	)		1,715,120
Total fixed maturity securities	$	12,011,336	$	552,430	$	(113,297	)	$	12,450,469
Equity securities	$	363,283	$	3,039	$	(2,586	)	$	363,736

Pre-Tax Cumulative Unrealized Appreciation (Depreciation) On Corporate Securities

	At December 31,
(Dollars in thousands)	2011		2010
Pre-tax cumulative unrealized appreciation (depreciation)	$	2,567	$	1,743

Summary Of Amortized Cost And Market Value Of Fixed Maturity Securities By Contractual Maturity

	At December 31, 2011				At December 31, 2010
	Amortized		Market		Amortized		Market
(Dollars in thousands)	Cost		Value		Cost		Value
Fixed maturity securities – available for sale:
Due in one year or less	$	494,098	$	494,911	$	572,985	$	580,528
Due after one year through five years		5,052,484		5,268,748		3,911,482		4,057,230
Due after five years through ten years		2,188,080		2,325,142		2,564,948		2,686,005
Due after ten years		1,246,886		1,354,208		2,331,639		2,402,163
Asset-backed securities		186,936		193,406		210,717		218,301
Mortgage-backed securities:
Commercial		310,387		321,427		324,922		337,219
Agency residential		2,198,937		2,282,593		2,018,384		2,093,282
Non-agency residential		53,365		53,089		76,259		75,741
Total fixed maturity securities	$	11,731,173	$	12,293,524	$	12,011,336	$	12,450,469

Summary Of Changes In Net Unrealized Appreciation (Depreciation) For The Company's Investments

	Years Ended December 31,
(Dollars in thousands)	2011			2010
Increase (decrease) during the period between the market value and cost
of investments carried at market value, and deferred taxes thereon:
Fixed maturity securities	$	122,393		$	40,095
Fixed maturity securities, other-than-temporary impairment		824			7,831
Equity securities		(15,143	)		(1,878	)
Other invested assets		(1,515	)		2,389
Change in unrealized appreciation (depreciation), pre-tax		106,559			48,437
Deferred tax benefit (expense)		(26,484	)		10,726
Deferred tax benefit (expense), other-than-temporary impairment		66			1,001
Change in unrealized appreciation (depreciation),
net of deferred taxes, included in shareholders' equity	$	80,141		$	60,164

Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities By Security Type

	Duration of Unrealized Loss at December 31, 2011 By Security Type
	Less than 12 months					Greater than 12 months					Total
			Gross					Gross					Gross
			Unrealized					Unrealized					Unrealized
(Dollars in thousands)	Market Value		Depreciation			Market Value		Depreciation			Market Value		Depreciation
Fixed maturity securities - available for sale
U.S. Treasury securities and obligations of
U.S. government agencies and corporations	$	-	$	-		$	3,452	$	(287	)	$	3,452	$	(287	)
Obligations of U.S. states and political subdivisions		-		-			7,518		(525	)		7,518		(525	)
Corporate securities		512,255		(14,962	)		120,064		(12,092	)		632,319		(27,054	)
Asset-backed securities		20,839		(339	)		3,655		(211	)		24,494		(550	)
Mortgage-backed securities
Commercial		9,292		(1,267	)		54,535		(8,635	)		63,827		(9,902	)
Agency residential		253,171		(2,524	)		43,894		(542	)		297,065		(3,066	)
Non-agency residential		1,542		(19	)		35,679		(756	)		37,221		(775	)
Foreign government securities		39,534		(1,035	)		132,977		(7,354	)		172,511		(8,389	)
Foreign corporate securities		278,949		(12,287	)		259,641		(19,902	)		538,590		(32,189	)
Total fixed maturity securities	$	1,115,582	$	(32,433	)	$	661,415	$	(50,304	)	$	1,776,997	$	(82,737	)
Equity securities		108,939		(8,499	)		204,466		(10,251	)		313,405		(18,750	)
Total	$	1,224,521	$	(40,932	)	$	865,881	$	(60,555	)	$	2,090,402	$	(101,487	)

	Duration of Unrealized Loss at December 31, 2010 By Security Type
	Less than 12 months					Greater than 12 months					Total
			Gross					Gross					Gross
			Unrealized					Unrealized					Unrealized
(Dollars in thousands)	Market Value		Depreciation			Market Value		Depreciation			Market Value		Depreciation
Fixed maturity securities - available for sale
U.S. Treasury securities and obligations of
U.S. government agencies and corporations	$	70,193	$	(2,425	)	$	43,264	$	(3,230	)	$	113,457	$	(5,655	)
Obligations of U.S. states and political subdivisions		336,522		(9,520	)		171,812		(15,409	)		508,334		(24,929	)
Corporate securities		186,898		(5,077	)		107,520		(11,441	)		294,418		(16,518	)
Asset-backed securities		7,816		(92	)		2,408		(123	)		10,224		(215	)
Mortgage-backed securities
Commercial		962		(25	)		58,036		(5,429	)		58,998		(5,454	)
Agency residential		208,930		(1,236	)		614		(233	)		209,544		(1,469	)
Non-agency residential		-		-			44,341		(1,723	)		44,341		(1,723	)
Foreign government securities		194,113		(6,416	)		203,913		(19,252	)		398,026		(25,668	)
Foreign corporate securities		309,627		(9,452	)		198,161		(22,214	)		507,788		(31,666	)
Total fixed maturity securities	$	1,315,061	$	(34,243	)	$	830,069	$	(79,054	)	$	2,145,130	$	(113,297	)
Equity securities		273,378		(2,584	)		13		(2	)		273,391		(2,586	)
Total	$	1,588,439	$	(36,827	)	$	830,082	$	(79,056	)	$	2,418,521	$	(115,883	)

Summary Of Aggregate Market Value And Gross Unrealized Depreciation Of Fixed Maturity And Equity Securities By Contractual Maturity

	Duration of Unrealized Loss at December 31, 2011 By Maturity
	Less than 12 months					Greater than 12 months					Total
			Gross					Gross					Gross
			Unrealized					Unrealized					Unrealized
(Dollars in thousands)	Market Value		Depreciation			Market Value		Depreciation			Market Value		Depreciation
Fixed maturity securities
Due in one year or less	$	26,581	$	(326	)	$	72,083	$	(8,953	)	$	98,664	$	(9,279	)
Due in one year through five years		421,995		(12,001	)		256,698		(15,635	)		678,693		(27,636	)
Due in five years through ten years		337,232		(13,019	)		159,476		(8,264	)		496,708		(21,283	)
Due after ten years		44,930		(2,938	)		35,395		(7,308	)		80,325		(10,246	)
Asset-backed securities		20,839		(339	)		3,655		(211	)		24,494		(550	)
Mortgage-backed securities		264,005		(3,810	)		134,108		(9,933	)		398,113		(13,743	)
Total fixed maturity securities	$	1,115,582	$	(32,433	)	$	661,415	$	(50,304	)	$	1,776,997	$	(82,737	)

	Duration of Unrealized Loss at December 31, 2010 By Maturity
	Less than 12 months					Greater than 12 months					Total
			Gross					Gross					Gross
			Unrealized					Unrealized					Unrealized
(Dollars in thousands)	Market Value		Depreciation			Market Value		Depreciation			Market Value		Depreciation
Fixed maturity securities
Due in one year or less	$	24,854	$	(450	)	$	55,204	$	(9,061	)	$	80,058	$	(9,511	)
Due in one year through five years		313,179		(11,829	)		224,770		(19,685	)		537,949		(31,514	)
Due in five years through ten years		358,468		(9,538	)		144,264		(12,624	)		502,732		(22,162	)
Due after ten years		400,852		(11,073	)		300,432		(30,176	)		701,284		(41,249	)
Asset-backed securities		7,816		(92	)		2,408		(123	)		10,224		(215	)
Mortgage-backed securities		209,892		(1,261	)		102,991		(7,385	)		312,883		(8,646	)
Total fixed maturity securities	$	1,315,061	$	(34,243	)	$	830,069	$	(79,054	)	$	2,145,130	$	(113,297	)

Components Of Net Investment Income

	Years Ended December 31,
(Dollars in thousands)	2011			2010			2009
Fixed maturity securities	$	521,991		$	581,870		$	570,798
Equity securities		57,573			12,200			3,574
Short-term investments and cash		1,281			151			5,965
Other invested assets
Limited partnerships		56,851			70,740			(19,022	)
Other		2,741			1,274			74
Total gross investment income		640,437			666,235			561,389
Interest debited (credited) and other investment expense		(20,396	)		(12,772	)		(13,596	)
Total net investment income	$	620,041		$	653,463		$	547,793

Components Of Net Realized Capital Gains (Losses)

	Years Ended December 31,
(Dollars in thousands)	2011			2010			2009
Fixed maturity securities, market value:
Other-than-temporary impairments	$	(16,223	)	$	(2,975	)	$	(13,210	)
Gains (losses) from sales		20,378			27,491			(45,666	)
Fixed maturity securities, fair value:
Gains (losses) from sales		(905	)		775			682
Gains (losses) from fair value adjustments		(15,518	)		15,091			9,337
Equity securities, market value:
Gains (losses) from sales		38			77			8,087
Equity securities, fair value:
Gains (losses) from sales		8,021			6,136			7,510
Gains (losses) from fair value adjustments		11,130			55,308			30,908
Short-term investments gain (loss)		2			8			40
Total net realized capital gains (losses)	$	6,923		$	101,911		$	(2,312	)

Proceeds And Split Between Gross Gains And Losses From Sales Of Fixed Maturity And Equity Securities

	Years Ended December 31,
(Dollars in thousands)	2011			2010			2009
Proceeds from sales of fixed maturity securities	$	1,797,404		$	1,652,956		$	326,050
Gross gains from sales		86,519			141,038			20,576
Gross losses from sales		(67,046	)		(112,772	)		(65,560	)
Proceeds from sales of equity securities	$	274,434		$	237,149		$	67,655
Gross gains from sales		16,325			11,562			16,483
Gross losses from sales		(8,266	)		(5,349	)		(886	)