Investment Securities - Investments in Debt and Equity Securities Reported Less than Historical Cost (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Fair value	$ 233,358	$ 72,390
Investments reported at less than historical cost:
Schedule of Investments [Line Items]
Historical cost	237,297	73,249
Fair value	$ 233,358	$ 72,390
Percent of the Corporation's available for sale and held to maturity portfolio	19.20%	6.10%