Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Gross unrealized losses and the fair value of the Company's investments
Fair Value less than 12 months	$ 183,690	$ 41,837
Unrealized losses less than 12 months	(5,839)	(168)
Fair value more than 12 months	1,141
Unrealized losses more than 12 months	(17)
Total fair value	184,831	41,837
Total unrealized losses	(5,856)	(168)
U.S. Treasury and federal agencies [Member]
Gross unrealized losses and the fair value of the Company's investments
Fair Value less than 12 months	27,871	13,064
Unrealized losses less than 12 months	(614)	(30)
Fair value more than 12 months
Unrealized losses more than 12 months
Total fair value	27,871	13,064
Total unrealized losses	(614)	(30)
State and municipal [Member]
Gross unrealized losses and the fair value of the Company's investments
Fair Value less than 12 months	55,862	11,928
Unrealized losses less than 12 months	(2,403)	(84)
Fair value more than 12 months	1,141
Unrealized losses more than 12 months	(17)
Total fair value	57,003	11,928
Total unrealized losses	(2,420)	(84)
Federal agency collateralized mortgage obligations [Member]
Gross unrealized losses and the fair value of the Company's investments
Fair Value less than 12 months	51,644	12,719
Unrealized losses less than 12 months	(1,170)	(39)
Fair value more than 12 months
Unrealized losses more than 12 months
Total fair value	51,644	12,719
Total unrealized losses	(1,170)	(39)
Federal agency mortgage-backed pools [Member]
Gross unrealized losses and the fair value of the Company's investments
Fair Value less than 12 months	48,313	4,126
Unrealized losses less than 12 months	(1,652)	(15)
Fair value more than 12 months
Unrealized losses more than 12 months
Total fair value	48,313	4,126
Total unrealized losses	$ (1,652)	$ (15)