Investment Securities - Investments in Debt and Equity Securities Reported Less than Historical Cost (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Fair value	$ 55,004	$ 72,390
Investments reported at less than historical cost:
Schedule of Investments [Line Items]
Historical cost	55,599	73,249
Fair value	$ 55,004	$ 72,390
Percent of the Corporation's available for sale and held to maturity portfolio	4.60%	6.10%