Securities in an Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Less than 12 Months	$ 815,924	$ 939,018
Gross Unrealized Losses, Less than 12 Months	8,724	18,853
Fair Value, 12 Months or Greater	374,005	460,375
Gross Unrealized Losses, 12 Months or Greater	35,482	73,449
Fair Value, Total	1,189,929	1,399,393
Gross Unrealized Losses, Total	44,206	92,302
U.S. Government And Government Agency [Member]
Fair Value, Less than 12 Months	51,405	24,668
Gross Unrealized Losses, Less than 12 Months	1,283	169
Fair Value, 12 Months or Greater	0	4,800
Gross Unrealized Losses, 12 Months or Greater	0	182
Fair Value, Total	51,405	29,468
Gross Unrealized Losses, Total	1,283	351
State And Municipal [Member]
Fair Value, Less than 12 Months	49,594	131,417
Gross Unrealized Losses, Less than 12 Months	558	827
Fair Value, 12 Months or Greater	184,408	183,205
Gross Unrealized Losses, 12 Months or Greater	14,304	15,723
Fair Value, Total	234,002	314,622
Gross Unrealized Losses, Total	14,862	16,550
Mortgage-Backed Securities [Member]
Fair Value, Less than 12 Months	259,508	172,729
Gross Unrealized Losses, Less than 12 Months	3,338	2,439
Fair Value, 12 Months or Greater	65,349	94,243
Gross Unrealized Losses, 12 Months or Greater	4,876	14,473
Fair Value, Total	324,857	266,972
Gross Unrealized Losses, Total	8,214	16,912
Corporate [Member]
Fair Value, Less than 12 Months	313,080	341,764
Gross Unrealized Losses, Less than 12 Months	1,784	8,327
Fair Value, 12 Months or Greater	78,646	125,654
Gross Unrealized Losses, 12 Months or Greater	14,003	27,760
Fair Value, Total	391,726	467,418
Gross Unrealized Losses, Total	15,787	36,087
Foreign [Member]
Fair Value, Less than 12 Months	101,200	197,560
Gross Unrealized Losses, Less than 12 Months	516	4,078
Fair Value, 12 Months or Greater	5,508	7,159
Gross Unrealized Losses, 12 Months or Greater	104	571
Fair Value, Total	106,708	204,719
Gross Unrealized Losses, Total	620	4,649
Fixed Maturity Securities [Member]
Fair Value, Less than 12 Months	774,787	868,138
Gross Unrealized Losses, Less than 12 Months	7,479	15,840
Fair Value, 12 Months or Greater	333,911	415,061
Gross Unrealized Losses, 12 Months or Greater	33,287	58,709
Fair Value, Total	1,108,698	1,283,199
Gross Unrealized Losses, Total	40,766	74,549
Common Stock [Member]
Fair Value, Less than 12 Months	34,702	47,098
Gross Unrealized Losses, Less than 12 Months	291	2,888
Fair Value, 12 Months or Greater	0	0
Gross Unrealized Losses, 12 Months or Greater	0	0
Fair Value, Total	34,702	47,098
Gross Unrealized Losses, Total	291	2,888
Preferred Stock [Member]
Fair Value, Less than 12 Months	6,435	23,782
Gross Unrealized Losses, Less than 12 Months	954	125
Fair Value, 12 Months or Greater	40,094	45,314
Gross Unrealized Losses, 12 Months or Greater	2,195	14,740
Fair Value, Total	46,529	69,096
Gross Unrealized Losses, Total	3,149	14,865
Equity Securities Available For Sale [Member]
Fair Value, Less than 12 Months	41,137	70,880
Gross Unrealized Losses, Less than 12 Months	1,245	3,013
Fair Value, 12 Months or Greater	40,094	45,314
Gross Unrealized Losses, 12 Months or Greater	2,195	14,740
Fair Value, Total	81,231	116,194
Gross Unrealized Losses, Total	$ 3,440	$ 17,753