Debt And Equity Securities (Gross Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	$ 574,566	$ 504,086
Unrealized losses, Less than 12 months	(3,928)	(54,109)
Estimated fair value, 12 months or longer	209,359	78,361
Unrealized losses, 12 months or longer	(29,872)	(12,136)
Estimated fair value, Total	783,925	582,447
Unrealized losses, Total	(33,800)	(66,245)
Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	573,753	372,318
Unrealized losses, Less than 12 months	(3,914)	(1,751)
Estimated fair value, 12 months or longer	63,568	78,361
Unrealized losses, 12 months or longer	(8,075)	(12,136)
Estimated fair value, Total	637,321	450,679
Unrealized losses, Total	(11,989)	(13,887)
U.S. Treasury Bonds [Member] | Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	44,552
Unrealized losses, Less than 12 months	(816)
Estimated fair value, 12 months or longer
Unrealized losses, 12 months or longer
Estimated fair value, Total	44,552
Unrealized losses, Total	(816)
Municipal Bonds [Member] | Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	34,495	7,186
Unrealized losses, Less than 12 months	(674)	(43)
Estimated fair value, 12 months or longer		1,896
Unrealized losses, 12 months or longer		(41)
Estimated fair value, Total	34,495	9,082
Unrealized losses, Total	(674)	(84)
Foreign Bonds [Member] | Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	78,545	30,508
Unrealized losses, Less than 12 months	(654)	(206)
Estimated fair value, 12 months or longer		690
Unrealized losses, 12 months or longer
Estimated fair value, Total	78,545	31,198
Unrealized losses, Total	(654)	(206)
Governmental Agency Bonds [Member] | Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	49,028	13,828
Unrealized losses, Less than 12 months	(373)	(1)
Estimated fair value, 12 months or longer		4,150
Unrealized losses, 12 months or longer
Estimated fair value, Total	49,028	17,978
Unrealized losses, Total	(373)	(1)
Governmental Agency Mortgage-Backed Securities [Member] | Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	330,281	280,114
Unrealized losses, Less than 12 months	(890)	(793)
Estimated fair value, 12 months or longer	39,156	43,835
Unrealized losses, 12 months or longer	(253)	(132)
Estimated fair value, Total	369,437	323,949
Unrealized losses, Total	(1,143)	(925)
Non-Agency Mortgage-Backed Securities [Member] | Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months
Unrealized losses, Less than 12 months
Estimated fair value, 12 months or longer	23,059	26,500
Unrealized losses, 12 months or longer	(7,805)	(11,933)
Estimated fair value, Total	23,059	26,500
Unrealized losses, Total	(7,805)	(11,933)
Corporate Debt Securities [Member] | Debt Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	36,852	40,682
Unrealized losses, Less than 12 months	(507)	(708)
Estimated fair value, 12 months or longer	1,353	1,290
Unrealized losses, 12 months or longer	(17)	(30)
Estimated fair value, Total	38,205	41,972
Unrealized losses, Total	(524)	(738)
Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Estimated fair value, Less than 12 months	813	131,768
Unrealized losses, Less than 12 months	(14)	(52,358)
Estimated fair value, 12 months or longer	145,791
Unrealized losses, 12 months or longer	(21,797)
Estimated fair value, Total	146,604	131,768
Unrealized losses, Total	$ (21,811)	$ (52,358)