Investment Securities HTM Securities Amortized Cost and Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investment securities held to maturity:
Investment securities held to maturity at amortized cost	$ 301,941	$ 175,210
Investment securities held to maturity, gross unrealized gains	6,875	401
Investment securities held to maturity, gross unrealized losses	(934)	(5,722)
Investment securities held to maturity, fair value	307,882	169,889
Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities held to maturity:
Investment securities held to maturity at amortized cost	301,941	175,210
Investment securities held to maturity, gross unrealized gains	6,875	401
Investment securities held to maturity, gross unrealized losses	(934)	(5,722)
Investment securities held to maturity, fair value	$ 307,882	$ 169,889