Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Amortized cost and fair value of securities held to maturity
Amortized Cost	$ 434,705	$ 412,075
Gross Unrealized Gains	14,928	7,911
Gross Unrealized Losses	(4,707)	(11,410)
Fair Value	444,926	408,576
Obligations of other U.S. Government agencies and corporations
Amortized cost and fair value of securities held to maturity
Amortized Cost	125,573	125,061
Gross Unrealized Gains	1	14
Gross Unrealized Losses	(4,336)	(8,727)
Fair Value	121,238	116,348
Obligations of states and political subdivisions
Amortized cost and fair value of securities held to maturity
Amortized Cost	309,132	287,014
Gross Unrealized Gains	14,927	7,897
Gross Unrealized Losses	(371)	(2,683)
Fair Value	$ 323,688	$ 292,228