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	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investment Securities [Abstract]
Balance, beginning of period	$ 10,500	$ 6,119	$ 549
Additions: Initial credit impairments	19,143	124	2,171
Additions: Subsequent credit impairments	825	4,518	3,747
Reductions: Accretion of credit loss impairment due to an increase in expected cash flows	(1,398)	(261)	(348)
Balance, end of period	$ 29,070	$ 10,500	$ 6,119