Securities in an Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Less than 12 Months	$ 939,018	$ 1,666,648
Gross Unrealized Losses, Less than 12 Months	18,853	40,632
Fair Value, 12 Months or Greater	460,375	569,902
Gross Unrealized Losses, 12 Months or Greater	73,449	66,040
Fair Value, Total	1,399,393	2,236,550
Gross Unrealized Losses, Total	92,302	106,672
U.S. Government And Government Agency [Member]
Fair Value, Less than 12 Months	24,668	60,228
Gross Unrealized Losses, Less than 12 Months	169	420
Fair Value, 12 Months or Greater	4,800	6,973
Gross Unrealized Losses, 12 Months or Greater	182	32
Fair Value, Total	29,468	67,201
Gross Unrealized Losses, Total	351	452
State and Municipal [Member]
Fair Value, Less than 12 Months	131,417	951,119
Gross Unrealized Losses, Less than 12 Months	827	26,577
Fair Value, 12 Months or Greater	183,205	156,617
Gross Unrealized Losses, 12 Months or Greater	15,723	18,840
Fair Value, Total	314,622	1,107,736
Gross Unrealized Losses, Total	16,550	45,417
Mortgage-Backed Securities [Member]
Fair Value, Less than 12 Months	172,729	116,194
Gross Unrealized Losses, Less than 12 Months	2,439	2,809
Fair Value, 12 Months or Greater	94,243	174,163
Gross Unrealized Losses, 12 Months or Greater	14,473	16,063
Fair Value, Total	266,972	290,357
Gross Unrealized Losses, Total	16,912	18,872
Corporate [Member]
Fair Value, Less than 12 Months	341,764	342,929
Gross Unrealized Losses, Less than 12 Months	8,327	6,581
Fair Value, 12 Months or Greater	125,654	155,259
Gross Unrealized Losses, 12 Months or Greater	27,760	22,798
Fair Value, Total	467,418	498,188
Gross Unrealized Losses, Total	36,087	29,379
Foreign [Member]
Fair Value, Less than 12 Months	197,560	110,189
Gross Unrealized Losses, Less than 12 Months	4,078	888
Fair Value, 12 Months or Greater	7,159	0
Gross Unrealized Losses, 12 Months or Greater	571	0
Fair Value, Total	204,719	110,189
Gross Unrealized Losses, Total	4,649	888
Fixed Maturity Securities [Member]
Fair Value, Less than 12 Months	868,138	1,580,659
Gross Unrealized Losses, Less than 12 Months	15,840	37,275
Fair Value, 12 Months or Greater	415,061	493,012
Gross Unrealized Losses, 12 Months or Greater	58,709	57,733
Fair Value, Total	1,283,199	2,073,671
Gross Unrealized Losses, Total	74,549	95,008
Common Stocks [Member]
Fair Value, Less than 12 Months	47,098	58,979
Gross Unrealized Losses, Less than 12 Months	2,888	989
Fair Value, 12 Months or Greater	0	0
Gross Unrealized Losses, 12 Months or Greater	0	0
Fair Value, Total	47,098	58,979
Gross Unrealized Losses, Total	2,888	989
Preferred Stocks [Member]
Fair Value, Less than 12 Months	23,782	27,010
Gross Unrealized Losses, Less than 12 Months	125	2,368
Fair Value, 12 Months or Greater	45,314	76,890
Gross Unrealized Losses, 12 Months or Greater	14,740	8,307
Fair Value, Total	69,096	103,900
Gross Unrealized Losses, Total	14,865	10,675
Equity Securities Available For Sale [Member]
Fair Value, Less than 12 Months	70,880	85,989
Gross Unrealized Losses, Less than 12 Months	3,013	3,357
Fair Value, 12 Months or Greater	45,314	76,890
Gross Unrealized Losses, 12 Months or Greater	14,740	8,307
Fair Value, Total	116,194	162,879
Gross Unrealized Losses, Total	$ 17,753	$ 11,664