Investment Securities (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2007
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Pledged securities, carrying value	$ 1,698,943,000	$ 1,230,358,000
Number of debt securities, held	50	142
Unrealized losses on debt securities, percent of amortized cost	0.50%	2.10%
Unrealized losses on debt securities, percent of Company's total amortized cost	0.10%	0.90%
Number of debt securities having unrealized losses	50	142
Number of securities recorded with an aggregate amortized cost	12	10
Number of securities, continuous unrealized loss position, twelve months or longer, fair value	12	10
Available-for-sale securities, amortized cost basis	24,453,000	22,822,000
Unrealized loss on securities	391,000	787,000
Warranted municipal revenue bond	$ 509,000	$ 517,000
Impairment of the par value bond, percentage	52.00%		10.00%
Fannie Mae And Freddie Mac Securities Rated AAA [Member]
Schedule of Securities Available-for-sale And Held To Maturity [Line Items]
Number of securities issued		10