Securities (Details) (USD $)	3 Months Ended	9 Months Ended
	Mar. 31, 2013	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Securities available-for-sale: [Abstract]
Amortized Cost		$ 703,714,000		$ 675,927,000
Gross Unrealized Gains		18,102,000		31,827,000
Gross Unrealized Losses		17,524,000		1,176,000
Fair Value		704,291,206		706,577,806
Securities pledged as collateral to secure public funds and other deposits or securities sold under agreements to repurchase		596,000,000
Available for sale securities, transfers	39,959,647	39,959,647	0
Securities held-to-maturity: [Abstract]
Amortized Cost		39,594,000		575,000
Gross Unrealized Gains		72,000		8,000
Gross Unrealized Losses		948,000		0
Fair Value		38,717,744		583,212	[1]
Available-for-sale, Amortized Cost [Abstract]
Due in one year or less		8,458,000
Due in one year to five years		26,415,000
Due in five years to ten years		143,804,000
Due after ten years		117,187,000
Mortgage-backed securities		390,179,000
Asset-backed securities		17,461,000
Amortized Cost		703,504,000
Available-for-sale, Fair Value [Abstract]
Due in one year or less		8,486,000
Due in one year to five years		27,000,000
Due in five years to ten years		144,830,000
Due after ten years		112,331,000
Mortgage-backed securities		394,330,000
Asset-backed securities		17,314,000
Fair Value		704,291,000
Held-to-maturity, Amortized Cost [Abstract]
Due in one year or less		320,000
Due in one year to five years		12,476,000
Due in five years to ten years		15,529,000
Due after ten years		11,269,000
Mortgage-backed securities		0
Amortized Cost		39,593,672		574,863
Asset-backed securities		0
Held-to-maturity, Fair Value [Abstract]
Due in one year or less		320,000
Due in one year to five years		12,465,000
Due in five years to ten years		15,127,000
Due after ten years		10,806,000
Mortgage-backed securities		0
Asset-backed securities		0
Fair Value		38,717,744		583,212	[1]
State and Municipal Securities [Member]
Securities held-to-maturity: [Abstract]
Amortized Cost		39,594,000		575,000
Gross Unrealized Gains		72,000		8,000
Gross Unrealized Losses		948,000		0
Fair Value				583,000
Held-to-maturity, Fair Value [Abstract]
Fair Value				583,000
US Treasury Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost		4,999,000		0
Gross Unrealized Gains		1,000		0
Gross Unrealized Losses		0		0
Fair Value		5,000,000		0
U.S. Government Agency Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost		137,908,000		110,817,000
Gross Unrealized Gains		225,000		49,000
Gross Unrealized Losses		10,642,000		414,000
Fair Value		127,491,000		110,452,000
Mortgage-backed Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost		390,179,000		360,504,000
Gross Unrealized Gains		10,142,000		15,770,000
Gross Unrealized Losses		5,991,000		623,000
Fair Value		394,330,000		375,651,000
State and Municipal Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost		142,943,000		177,364,000
Gross Unrealized Gains		6,581,000		14,489,000
Gross Unrealized Losses		734,000		126,000
Fair Value		148,790,000		191,727,000
Asset-backed Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost		17,461,000		17,361,000
Gross Unrealized Gains		0		0
Gross Unrealized Losses		147,000		9,000
Fair Value		17,314,000		17,352,000
Corporate Notes and Other [Member]
Securities available-for-sale: [Abstract]
Amortized Cost		10,224,000		9,881,000
Gross Unrealized Gains		1,153,000		1,519,000
Gross Unrealized Losses		10,000		4,000
Fair Value		$ 11,367,000		$ 11,396,000

[1] Estimated fair values are consistent with an exit-price concept. The assumptions used to estimate the fair values are intended to approximate those that a market-participant would realize in a hypothetical orderly transaction.