Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Scheduled maturities of securities
Weighted Average Yield, Due in one year or less	3.93%	4.65%
Amortized cost, Due in one year or less	$ 21,514	$ 43,232
Fair value, Due in one year or less	21,820	43,644
Weighted Average Yield, Due from one year to five years	3.18%	3.62%
Amortized cost, Due from one year to five years	174,718	106,858
Fair value, Due from one year to five years	181,660	107,452
Weighted Average Yield, Due from five to ten years	3.79%	5.03%
Amortized cost, Due from five to ten years	101,673	102,525
Fair value, Due from five to ten years	105,645	106,384
Weighted Average Yield, Due after ten years	3.44%	3.74%
Amortized cost, Due after ten years	785,894	837,128
Fair value, Due after ten years	825,555	870,533
Weighted Average Yield, Total	3.44%	3.89%
Amortized cost, Total	1,083,799	1,089,743
Fair value, Total	$ 1,134,680	$ 1,128,013