Investment Securities (Investments in Debt and Equity Securities Reported Less than Historical Cost) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Investments [Line Items]
Fair value	$ 38,221	$ 17,038
Investments in Debt and Equity Securities, Reported at Less than Historical Cost
Schedule of Investments [Line Items]
Historical cost	44,428	22,999
Fair value	$ 38,221	$ 17,038
Percent of the Corporation's available for sale and held to maturity portfolio	4.40%	1.90%