Investment Securities (Rollforward Of Total Amount Of Credit-Related OTTI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	$ (314,342)		$ (317,710)		$ (320,986)		$ (341,039)
Credit-related OTTI not previously recognized	(341)	[1]			(341)	[1]
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis	(6,967)	[2]	(5,158)	[2]	(17,176)	[2]	(8,263)	[2]
Subtotal of amounts recognized in earnings	7,308		5,158		17,517		8,263
Reductions for securities sold during the period	0		27,302		16,853		53,736
Balance of credit-related OTTI at end of period	(321,650)		(295,566)		(321,650)		(295,566)
Held-To-Maturity [Member]
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	(6,126)		(5,357)		(6,126)		(5,357)
Credit-related OTTI not previously recognized	(341)	[1]			(341)	[1]
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis	0	[2]	0	[2]	0	[2]	0	[2]
Subtotal of amounts recognized in earnings	341		0		341		0
Balance of credit-related OTTI at end of period	(6,467)		(5,357)		(6,467)		(5,357)
Available-for-sale Securities [Member]
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	(308,216)		(312,353)		(314,860)		(335,682)
Credit-related OTTI not previously recognized	0	[1]			0	[1]
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis	(6,967)	[2]	(5,158)	[2]	(17,176)	[2]	(8,263)	[2]
Subtotal of amounts recognized in earnings	6,967		5,158		17,176		8,263
Reductions for securities sold during the period	0		27,302		16,853		53,736
Balance of credit-related OTTI at end of period	$ (315,183)		$ (290,209)		$ (315,183)		$ (290,209)

[1] Relates to securities not previously impaired.

[2] Relates to additional impairment on securities previously impaired.