Commercial Paper and Other Short-Term Borrowings (Details Textual)	Jun. 30, 2012	Dec. 31, 2011
Federal Funds Purchased and Securities Sold Under Agreements To Repurchase [Member]
Commercial paper and other short-term borrowings (Textual) [Abstract]
Commercial paper and other short-term borrowings, Weighted average interest rate	0.22%	0.06%
Commercial paper [Member]
Commercial paper and other short-term borrowings (Textual) [Abstract]
Commercial paper and other short-term borrowings, Weighted average interest rate	0.28%	0.22%
Federal Funds Purchased [Member]
Commercial paper and other short-term borrowings (Textual) [Abstract]
Commercial paper and other short-term borrowings, Weighted average interest rate		0.15%
Fixed and floating rate Federal Home Loan Bank advances with maturities ranging from January 2013 to February 2016 [Member]
Commercial paper and other short-term borrowings (Textual) [Abstract]
Commercial paper and other short-term borrowings, Weighted average interest rate		0.48%
Other Borrowed Funds [Member]
Commercial paper and other short-term borrowings (Textual) [Abstract]
Commercial paper and other short-term borrowings, Weighted average interest rate		0.73%