Investment Securities (Rollforward Of Total Amount Of Credit-Related OTTI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	$ (320,986)		$ (341,039)
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis	(10,209)	[1]	(3,105)	[1]
Subtotal of amounts recognized in earnings	(10,209)		(3,105)
Reductions for securities sold during the period	16,853		26,434
Balance of credit-related OTTI at end of period	(314,342)		(317,710)
Held-To-Maturity [Member]
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	(6,126)		(5,357)
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis		[1]		[1]
Subtotal of amounts recognized in earnings
Balance of credit-related OTTI at end of period	(6,126)		(5,357)
Available-For-Sale Securities [Member]
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	(314,860)		(335,682)
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis	(10,209)	[1]	(3,105)	[1]
Subtotal of amounts recognized in earnings	(10,209)		(3,105)
Reductions for securities sold during the period	16,853		26,434
Balance of credit-related OTTI at end of period	$ (308,216)		$ (312,353)

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