Securities in an Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Less than 12 Months	$ 823,414	$ 939,018
Gross Unrealized Losses, Less than 12 Months	13,470	18,853
Fair Value, 12 Months or Greater	399,683	460,375
Gross Unrealized Losses, 12 Months or Greater	49,919	73,449
Fair Value, Total	1,223,097	1,399,393
Gross Unrealized Losses, Total	63,389	92,302
U.S. Government And Government Agency [Member]
Fair Value, Less than 12 Months	18,412	24,668
Gross Unrealized Losses, Less than 12 Months	126	169
Fair Value, 12 Months or Greater	0	4,800
Gross Unrealized Losses, 12 Months or Greater	0	182
Fair Value, Total	18,412	29,468
Gross Unrealized Losses, Total	126	351
State And Municipal [Member]
Fair Value, Less than 12 Months	118,623	131,417
Gross Unrealized Losses, Less than 12 Months	977	827
Fair Value, 12 Months or Greater	206,125	183,205
Gross Unrealized Losses, 12 Months or Greater	15,296	15,723
Fair Value, Total	324,748	314,622
Gross Unrealized Losses, Total	16,273	16,550
Mortgage-Backed Securities [Member]
Fair Value, Less than 12 Months	281,422	172,729
Gross Unrealized Losses, Less than 12 Months	2,358	2,439
Fair Value, 12 Months or Greater	62,418	94,243
Gross Unrealized Losses, 12 Months or Greater	8,973	14,473
Fair Value, Total	343,840	266,972
Gross Unrealized Losses, Total	11,331	16,912
Corporate [Member]
Fair Value, Less than 12 Months	215,838	341,764
Gross Unrealized Losses, Less than 12 Months	1,997	8,327
Fair Value, 12 Months or Greater	84,614	125,654
Gross Unrealized Losses, 12 Months or Greater	17,907	27,760
Fair Value, Total	300,452	467,418
Gross Unrealized Losses, Total	19,904	36,087
Foreign [Member]
Fair Value, Less than 12 Months	103,524	197,560
Gross Unrealized Losses, Less than 12 Months	4,112	4,078
Fair Value, 12 Months or Greater	7,959	7,159
Gross Unrealized Losses, 12 Months or Greater	271	571
Fair Value, Total	111,483	204,719
Gross Unrealized Losses, Total	4,383	4,649
Fixed Maturity Securities [Member]
Fair Value, Less than 12 Months	737,819	868,138
Gross Unrealized Losses, Less than 12 Months	9,570	15,840
Fair Value, 12 Months or Greater	361,116	415,061
Gross Unrealized Losses, 12 Months or Greater	42,447	58,709
Fair Value, Total	1,098,935	1,283,199
Gross Unrealized Losses, Total	52,017	74,549
Common Stock [Member]
Fair Value, Less than 12 Months	62,293	47,098
Gross Unrealized Losses, Less than 12 Months	2,415	2,888
Fair Value, 12 Months or Greater	0	0
Gross Unrealized Losses, 12 Months or Greater	0	0
Fair Value, Total	62,293	47,098
Gross Unrealized Losses, Total	2,415	2,888
Preferred Stock [Member]
Fair Value, Less than 12 Months	23,302	23,782
Gross Unrealized Losses, Less than 12 Months	1,485	125
Fair Value, 12 Months or Greater	38,567	45,314
Gross Unrealized Losses, 12 Months or Greater	7,472	14,740
Fair Value, Total	61,869	69,096
Gross Unrealized Losses, Total	8,957	14,865
Equity Securities Available For Sale [Member]
Fair Value, Less than 12 Months	85,595	70,880
Gross Unrealized Losses, Less than 12 Months	3,900	3,013
Fair Value, 12 Months or Greater	38,567	45,314
Gross Unrealized Losses, 12 Months or Greater	7,472	14,740
Fair Value, Total	124,162	116,194
Gross Unrealized Losses, Total	$ 11,372	$ 17,753