Deposits and Borrowed Funds (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Federal funds purchased, securities sold under repurchase agreements, and other short term borrowings
Balances at Year-end	$ 50,000	$ 620	$ 627,469
Average Balance	3,839	164,020	466,970
Average Rate (as a percent)	0.06%	3.23%	1.85%
Federal funds purchased
Federal funds purchased, securities sold under repurchase agreements, and other short term borrowings
Balances at Year-end	50,000		426,779
Average Balance	3,145	29,131	214,672
Average Rate (as a percent)	0.07%	0.10%	0.16%
Maximum month-end balance	100,000	99,394	689,202
Securities sold under repurchase agreements
Federal funds purchased, securities sold under repurchase agreements, and other short term borrowings
Balances at Year-end			200,000
Average Balance		134,178	200,000
Average Rate (as a percent)		3.92%	3.98%
Maximum month-end balance		200,000	200,000
Other short-term borrowings
Federal funds purchased, securities sold under repurchase agreements, and other short term borrowings
Balances at Year-end		620	690
Average Balance	694	711	52,298
Average Rate (as a percent)		0.08%	0.63%
Maximum month-end balance	$ 720	$ 750	$ 121,859