Investment Securities (Narrative) (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010
Pledged securities, carrying value	$ 1,543,819,000	$ 1,230,358,000
Number of debt securities, held	147	142
Unrealized losses on debt securities, percent	1.00%	2.10%
Total amortized cost, percent	0.20%	0.90%
Number of unrealized loss securities relate to market interest rate changes	147	142
Number of securities aggregate amortized cost basis	7	10
Number of securities, continuous unrealized loss position, twelve months or longer, fair value	7	10
Available-for-sale securities, amortized cost basis	19,387,000	22,822,000
Unrealized loss on securities	$ 416,000	$ 787,000
Fannie Mae And Freddie Mac Securities Are Rated AAA [Member]
Number of securities issued	7	10