Investment Securities (Changes In The Credit Loss Component Of Cumulative Other-Than-Temporary Impairment Losses On Debt Securities) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Investment Securities [Abstract]
Balance, beginning of period	$ 29,070	$ 10,500
Additions: Subsequent credit impairments		825
Reductions: Accretion of credit loss impairment due to an increase in expected cash flows	(303)	(156)
Balance, end of period	$ 28,767	$ 11,169