Federal Funds Purchased (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Federal funds	$ 0	$ 0
Federal home loan bank, advances, general debt obligations, disclosures, amount of available, unused funds	1,800,000,000
Maximum [Member]
Interest rate available lines of credit	3.00%
Minimum [Member]
Interest rate available lines of credit	0.30%
Federal Reserve [Member]
Lines of credit	448,500,000
Federal Funds Purchased [Member]
Lines of credit	$ 135,000,000