Securities In An Unrealized Loss Position Securities in an Unrealized Loss Position (Securities in an Unrealized Loss Position) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 1,590,409	$ 3,085,977
Gross Unrealized Losses, Less than 12 Months	11,343	84,259
Fair Value, 12 Months or Greater	968,927	355,098
Gross Unrealized Losses, 12 Months or Greater	46,922	33,194
Fair Value, Total	2,559,336	3,441,075
Gross Unrealized Losses, Total	58,265	117,453
U.S. government and government agency
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	131,471	260,882
Gross Unrealized Losses, Less than 12 Months	1,411	7,927
Fair Value, 12 Months or Greater	85,253	2,163
Gross Unrealized Losses, 12 Months or Greater	3,818	55
Fair Value, Total	216,724	263,045
Gross Unrealized Losses, Total	5,229	7,982
State and municipal
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	111,019	899,613
Gross Unrealized Losses, Less than 12 Months	743	24,503
Fair Value, 12 Months or Greater	175,757	87,345
Gross Unrealized Losses, 12 Months or Greater	4,076	5,334
Fair Value, Total	286,776	986,958
Gross Unrealized Losses, Total	4,819	29,837
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	182,774	578,603
Gross Unrealized Losses, Less than 12 Months	1,481	17,964
Fair Value, 12 Months or Greater	295,503	140,648
Gross Unrealized Losses, 12 Months or Greater	12,811	8,965
Fair Value, Total	478,277	719,251
Gross Unrealized Losses, Total	14,292	26,929
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	1,068,868	1,013,373
Gross Unrealized Losses, Less than 12 Months	3,983	17,066
Fair Value, 12 Months or Greater	269,171	105,074
Gross Unrealized Losses, 12 Months or Greater	13,025	13,034
Fair Value, Total	1,338,039	1,118,447
Gross Unrealized Losses, Total	17,008	30,100
Foreign government
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	82,459	320,215
Gross Unrealized Losses, Less than 12 Months	3,154	16,286
Fair Value, 12 Months or Greater	120,708	0
Gross Unrealized Losses, 12 Months or Greater	10,053	0
Fair Value, Total	203,167	320,215
Gross Unrealized Losses, Total	13,207	16,286
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	1,576,591	3,072,686
Gross Unrealized Losses, Less than 12 Months	10,772	83,746
Fair Value, 12 Months or Greater	946,392	335,230
Gross Unrealized Losses, 12 Months or Greater	43,783	27,388
Fair Value, Total	2,522,983	3,407,916
Gross Unrealized Losses, Total	54,555	111,134
Common stocks
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	10,813	0
Gross Unrealized Losses, Less than 12 Months	531	0
Fair Value, 12 Months or Greater	0	0
Gross Unrealized Losses, 12 Months or Greater	0	0
Fair Value, Total	10,813	0
Gross Unrealized Losses, Total	531	0
Preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	3,005	13,291
Gross Unrealized Losses, Less than 12 Months	40	513
Fair Value, 12 Months or Greater	22,535	19,868
Gross Unrealized Losses, 12 Months or Greater	3,139	5,806
Fair Value, Total	25,540	33,159
Gross Unrealized Losses, Total	3,179	6,319
Equity securities available for sale
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	13,818	13,291
Gross Unrealized Losses, Less than 12 Months	571	513
Fair Value, 12 Months or Greater	22,535	19,868
Gross Unrealized Losses, 12 Months or Greater	3,139	5,806
Fair Value, Total	36,353	33,159
Gross Unrealized Losses, Total	$ 3,710	$ 6,319