Investment Securities (Rollforward Of Total Amount Of Credit-Related OTTI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	$ (321,650)		$ (295,566)		$ (320,986)		$ (341,039)
Credit-related OTTI not previously recognized	0	[1]	(3,776)	[1]	(341)	[1]	(3,776)	[1]
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis	(2,736)	[2]	(9,558)	[2]	(19,912)	[2]	(17,821)	[2]
Subtotal of amounts recognized in earnings	2,736		13,334		20,253		21,597
Reductions for securities sold during the period	0		0		16,853		53,736
Balance of credit-related OTTI at end of period	(324,386)		(308,900)		(324,386)		(308,900)
Held-To-Maturity [Member]
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	(6,467)		(5,357)		(6,126)		(5,357)
Credit-related OTTI not previously recognized	0	[1]	(769)	[1]	(341)	[1]	(769)	[1]
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis	(657)	[2]	0	[2]	(657)	[2]	0	[2]
Subtotal of amounts recognized in earnings	657		769		998		769
Balance of credit-related OTTI at end of period	(7,124)		(6,126)		(7,124)		(6,126)
Available-for-sale Securities [Member]
Investment [Line Items]
Balance of credit-related OTTI at beginning of period	(315,183)		(290,209)		(314,860)		(335,682)
Credit-related OTTI not previously recognized	0	[1]	(3,007)	[1]	0	[1]	(3,007)	[1]
Credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost basis	(2,079)	[2]	(9,558)	[2]	(19,255)	[2]	(17,821)	[2]
Subtotal of amounts recognized in earnings	2,079		12,565		19,255		20,828
Reductions for securities sold during the period	0		0		16,853		53,736
Balance of credit-related OTTI at end of period	$ (317,262)		$ (302,774)		$ (317,262)		$ (302,774)

[1] Relates to securities not previously impaired.

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