Investment Securities Summary of Cumulative Other-than-Temporary Impairment Charges Recognized in Earnings for Pooled Trust Preferred Securities Held (Details) (Pooled Trust Preferred Securities [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Pooled Trust Preferred Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance of cumulative credit losses on pooled trust preferred securities, beginning of period	$ (27,560)	$ (15,612)
Additions for credit losses recorded which were not previously recognized as components of earnings	(1,698)	(11,969)
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	6,400	0
Reductions for increases in cash flows expected to be collected that are recognized over the remaining life of the security	77	21
Balance of cumulative credit losses on pooled trust preferred securities, end of period	$ (22,781)	$ (27,560)