Investment Securities (Narrative) (Details Textual) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Investments, Debt and Equity Securities [Abstract]
Maximum portfolio concentration in municipal securities per corporate investment policy	20.00%
Revenue bonds, number owned by corporation	1
Revenue bond, fair value	$ 600,000
Revenue bond, amortized cost	500,000
General obligation bonds, fair market value adjustment	600,000
Investment Securities
Other investment securities pledged	$ 3,400,000,000	$ 1,600,000,000	$ 1,900,000,000
Amount of municipal securities with a combined individual state to total municipal outstanding equal to or less than, per corporate policy	25.00%