Investment Securities Summary of Cumulative Other-than-Temporary Impairment Charges Recognized in Earnings for Pooled Trust Preferred Securities Held (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance of cumulative credit losses on pooled trust preferred securities, beginning of period	$ (28,876)	$ (22,754)	$ (27,560)	$ (15,612)
Additions for credit losses recorded which were not previously recognized as components of earnings	(345)	(2,335)	(1,698)	(9,477)
Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security	40	21	77	21
Balance of cumulative credit losses on pooled trust preferred securities, end of period	$ (29,181)	$ (25,068)	$ (29,181)	$ (25,068)