Other Borrowings (Details Textual) (USD $)			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Other collateralized borrowings, fixed rate, as of March 31, 2013 of 0.05% payable on April 1, 2013 [Member]
Other Borrowings (Textual) [Abstract]
FHLB fixed rate borrowings effective rate			0.05%
FHLB fixed rate borrowings maturity date			Apr. 01, 2013
Other Borrowings (Additional Textual) [Abstract]
Other collateralized borrowings	$ 8,125,000	$ 9,197,000
Repurchase investment securities sold and pledged as collateral under securities repurchase agreement	8,125,000
FHLB Collateral line of credit, maximum borrowings capacity	511,625,000
FHLB collateral line of credit, outstanding balance	0
FHLB collateral line of credit, remaining borrowing capacity	511,625,000
Loans designated as potential collateral under collateralized line of credit with FHLB	1,006,023,000
Collateralized line of credit with Federal Reserve Bank, maximum borrowings capacity	80,091,000
Collateralized line of credit with Federal Reserve Bank, outstanding balance	0
Collateralized line of credit with Federal Reserve Bank, remaining borrowing capacity	80,091,000
Investment securities designated as potential collateral under collateral line of credit with FRB	54,000
Loans designated as potential collateral under collateral line of credit with FRB	102,267,000
Unused correspondent banking lines of credit from commercial banks for federal funds	$ 5,000,000