Deposits and Borrowed Funds (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Federal funds purchased, securities sold under repurchase agreements, and other short term borrowings
Balances at Year-end	$ 1,214,200	$ 50,000	$ 620
Average Balance	52,051	3,839	164,020
Average interest rate (as a percent)	0.09%	0.06%	3.23%
Federal funds purchased
Federal funds purchased, securities sold under repurchase agreements, and other short term borrowings
Balances at Year-end	1,214,200	50,000
Average Balance	52,051	3,145	29,131
Average interest rate (as a percent)	0.09%	0.07%	0.10%
Maximum month-end balance	1,214,200	100,000	99,394
Securities sold under repurchase agreements
Federal funds purchased, securities sold under repurchase agreements, and other short term borrowings
Average Balance			134,178
Average interest rate (as a percent)			3.92%
Maximum month-end balance			200,000
Other short-term borrowings
Federal funds purchased, securities sold under repurchase agreements, and other short term borrowings
Balances at Year-end			620
Average Balance		694	711
Average interest rate (as a percent)			0.08%
Maximum month-end balance		$ 720	$ 750