Securities in an Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Less than 12 Months	$ 961,911	$ 939,018
Gross Unrealized Losses, Less than 12 Months	11,106	18,853
Fair Value, 12 Months or Greater	412,000	460,375
Gross Unrealized Losses, 12 Months or Greater	53,220	73,449
Fair Value, Total	1,373,911	1,399,393
Gross Unrealized Losses, Total	64,326	92,302
U.S. Government And Government Agency [Member]
Fair Value, Less than 12 Months	37,262	24,668
Gross Unrealized Losses, Less than 12 Months	420	169
Fair Value, 12 Months or Greater	0	4,800
Gross Unrealized Losses, 12 Months or Greater	0	182
Fair Value, Total	37,262	29,468
Gross Unrealized Losses, Total	420	351
State And Municipal [Member]
Fair Value, Less than 12 Months	157,870	131,417
Gross Unrealized Losses, Less than 12 Months	4,768	827
Fair Value, 12 Months or Greater	163,499	183,205
Gross Unrealized Losses, 12 Months or Greater	13,832	15,723
Fair Value, Total	321,369	314,622
Gross Unrealized Losses, Total	18,600	16,550
Mortgage-Backed Securities [Member]
Fair Value, Less than 12 Months	211,782	172,729
Gross Unrealized Losses, Less than 12 Months	1,736	2,439
Fair Value, 12 Months or Greater	90,061	94,243
Gross Unrealized Losses, 12 Months or Greater	10,814	14,473
Fair Value, Total	301,843	266,972
Gross Unrealized Losses, Total	12,550	16,912
Corporate [Member]
Fair Value, Less than 12 Months	294,902	341,764
Gross Unrealized Losses, Less than 12 Months	2,138	8,327
Fair Value, 12 Months or Greater	110,709	125,654
Gross Unrealized Losses, 12 Months or Greater	21,886	27,760
Fair Value, Total	405,611	467,418
Gross Unrealized Losses, Total	24,024	36,087
Foreign [Member]
Fair Value, Less than 12 Months	186,669	197,560
Gross Unrealized Losses, Less than 12 Months	1,230	4,078
Fair Value, 12 Months or Greater	8,336	7,159
Gross Unrealized Losses, 12 Months or Greater	44	571
Fair Value, Total	195,005	204,719
Gross Unrealized Losses, Total	1,274	4,649
Fixed Maturity Securities [Member]
Fair Value, Less than 12 Months	888,485	868,138
Gross Unrealized Losses, Less than 12 Months	10,292	15,840
Fair Value, 12 Months or Greater	372,605	415,061
Gross Unrealized Losses, 12 Months or Greater	46,576	58,709
Fair Value, Total	1,261,090	1,283,199
Gross Unrealized Losses, Total	56,868	74,549
Common Stock [Member]
Fair Value, Less than 12 Months	47,310	47,098
Gross Unrealized Losses, Less than 12 Months	735	2,888
Fair Value, 12 Months or Greater	0	0
Gross Unrealized Losses, 12 Months or Greater	0	0
Fair Value, Total	47,310	47,098
Gross Unrealized Losses, Total	735	2,888
Preferred Stock [Member]
Fair Value, Less than 12 Months	26,116	23,782
Gross Unrealized Losses, Less than 12 Months	79	125
Fair Value, 12 Months or Greater	39,395	45,314
Gross Unrealized Losses, 12 Months or Greater	6,644	14,740
Fair Value, Total	65,511	69,096
Gross Unrealized Losses, Total	6,723	14,865
Equity Securities Available For Sale [Member]
Fair Value, Less than 12 Months	73,426	70,880
Gross Unrealized Losses, Less than 12 Months	814	3,013
Fair Value, 12 Months or Greater	39,395	45,314
Gross Unrealized Losses, 12 Months or Greater	6,644	14,740
Fair Value, Total	112,821	116,194
Gross Unrealized Losses, Total	$ 7,458	$ 17,753