Securities (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Securities available-for-sale [Abstract]
Amortized Cost	$ 733,602,000	$ 700,492,000
Gross Unrealized Gains	20,802,000	16,306,000
Gross Unrealized Losses	10,876,000	23,342,000
Fair Value	743,528,294	693,456,314
Securities pledged as collateral to secure public funds and other deposits or securities sold under agreements to repurchase	619,100,000
Securities held-to-maturity [Abstract]
Amortized Cost	38,538,000	39,796,000
Gross Unrealized Gains	120,000	72,000
Gross Unrealized Losses	368,000	1,051,000
Fair Value	38,290,464	38,817,467
Available-for-sale, Amortized Cost [Abstract]
Due in one year or less	4,124,000
Due in one year to five years	33,208,000
Due in five years to ten years	125,395,000
Due after ten years	102,915,000
Mortgage-backed securities	452,580,000
Asset-backed securities	15,380,000
Amortized Cost	733,602,000
Available-for-sale, Fair Value [Abstract]
Due in one year or less	4,161,000
Due in one year to five years	34,896,000
Due in five years to ten years	128,613,000
Due after ten years	100,690,000
Mortgage-backed securities	459,938,000
Asset-backed securities	15,230,000
Fair Value	743,528,000
Held-to-maturity, Amortized Cost [Abstract]
Due in one year or less	658,000
Due in one year to five years	8,184,000
Due in five years to ten years	12,578,000
Due after ten years	17,118,000
Mortgage-backed securities	0
Asset-backed securities	0
Amortized Cost	38,537,545	39,795,649
Held-to-maturity, Fair Value [Abstract]
Due in one year or less	660,000
Due in one year to five years	8,107,000
Due in five years to ten years	12,632,000
Due after ten years	16,891,000
Mortgage-backed securities	0
Asset-backed securities	0
Fair Value	38,290,464	38,817,467
State and Municipal Securities [Member]
Securities held-to-maturity [Abstract]
Amortized Cost	38,538,000	39,796,000
Gross Unrealized Gains	120,000	72,000
Gross Unrealized Losses	368,000	1,051,000
Fair Value	38,290,000	38,817,000
Held-to-maturity, Fair Value [Abstract]
Fair Value	38,290,000	38,817,000
US Treasury Securities [Member]
Securities available-for-sale [Abstract]
Amortized Cost	0	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	0	0
U.S. Government Agency Securities [Member]
Securities available-for-sale [Abstract]
Amortized Cost	117,053,000	117,282,000
Gross Unrealized Gains	19,000	13,000
Gross Unrealized Losses	6,148,000	13,422,000
Fair Value	110,924,000	103,873,000
Mortgage-backed Securities [Member]
Securities available-for-sale [Abstract]
Amortized Cost	452,580,000	411,967,000
Gross Unrealized Gains	11,608,000	9,771,000
Gross Unrealized Losses	4,250,000	8,802,000
Fair Value	459,938,000	412,936,000
State and Municipal Securities [Member]
Securities available-for-sale [Abstract]
Amortized Cost	138,382,000	143,763,000
Gross Unrealized Gains	8,066,000	5,504,000
Gross Unrealized Losses	328,000	856,000
Fair Value	146,120,000	148,411,000
Asset-backed Securities [Member]
Securities available-for-sale [Abstract]
Amortized Cost	15,380,000	17,262,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	150,000	255,000
Fair Value	15,230,000	17,007,000
Corporate Notes and Other [Member]
Securities available-for-sale [Abstract]
Amortized Cost	10,207,000	10,218,000
Gross Unrealized Gains	1,109,000	1,018,000
Gross Unrealized Losses	0	7,000
Fair Value	$ 11,316,000	$ 11,229,000