Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Amortized cost and fair value of securities held to maturity
Amortized Cost	$ 438,283	$ 412,075
Gross Unrealized Gains	13,401	7,911
Gross Unrealized Losses	(5,417)	(11,410)
Fair Value	446,267	408,576
Obligations of other U.S. Government agencies and corporations
Amortized cost and fair value of securities held to maturity
Amortized Cost	125,566	125,061
Gross Unrealized Gains	14	14
Gross Unrealized Losses	(4,644)	(8,727)
Fair Value	120,936	116,348
Obligations of states and political subdivisions
Amortized cost and fair value of securities held to maturity
Amortized Cost	312,717	287,014
Gross Unrealized Gains	13,387	7,897
Gross Unrealized Losses	(773)	(2,683)
Fair Value	$ 325,331	$ 292,228