Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Securities available-for-sale: [Abstract]
Amortized Cost	$ 1,310,071,000	$ 930,708,000
Gross Unrealized Gains	8,557,000	13,642,000
Gross Unrealized Losses	20,082,000	9,285,000
Fair Value	1,298,546,056	935,064,745
Available-for-sale, Amortized Cost [Abstract]
Due in one year or less	2,533,000
Due in one year to five years	60,311,000
Due in five years to ten years	122,753,000
Due after ten years	57,148,000
Mortgage-backed securities	988,008,000
Asset-backed securities	79,318,000
Amortized Cost	1,310,071,000
Available-for-sale, Fair Value [Abstract]
Due in one year or less	2,556,000
Due in one year to five years	61,591,000
Due in five years to ten years	123,769,000
Due after ten years	55,424,000
Mortgage-backed securities	976,626,000
Asset-backed securities	78,580,000
Fair Value	1,298,546,056
Securities pledged as collateral to secure public funds and other deposits or securities sold under agreements to repurchase	902,900,000
Secured borrowing under agreement to repurchase	85,700,000
Available for Sale Securities Transferred to Held To Maturity Securities		0
Proceeds from sale of available-for-sale securities	72,829,440	189,029,458	$ 2,360,478
Investment gains on sales	395,186	552,063	$ 29,221
Securities held-to-maturity: [Abstract]
Amortized Cost	25,251,316	31,376,840
Gross Unrealized Gains	87,000	257,000
Gross Unrealized Losses	105,000	48,000
Fair Value	25,233,254	31,585,303
Held-to-maturity, Amortized Cost [Abstract]
Due in one year or less	594,000
Due in one year to five years	10,186,000
Due in five years to ten years	10,586,000
Due after ten years	3,885,000
Mortgage-backed securities	0
Asset-backed securities	0
Amortized Cost	25,251,316	31,376,840
Held-to-maturity, Fair Value [Abstract]
Due in one year or less	594,000
Due in one year to five years	10,182,000
Due in five years to ten years	10,567,000
Due after ten years	3,890,000
Mortgage-backed securities	0
Asset-backed securities	0
Fair Value	25,233,254	31,585,303
Securities Pledged as Collateral [Member]
Available-for-sale, Fair Value [Abstract]
Secured borrowing under agreement to repurchase	85,700,000
US Treasury Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost	250,000	0
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	250,000	0
U.S. Government Agency Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost	22,306,000	131,499,000
Gross Unrealized Gains	0	3,000
Gross Unrealized Losses	537,000	3,309,000
Fair Value	21,769,000	128,193,000
Mortgage-backed Agency Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost	988,008,000	581,998,000
Gross Unrealized Gains	4,304,000	5,948,000
Gross Unrealized Losses	15,686,000	5,030,000
Fair Value	976,626,000	582,916,000
State and Municipal Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost	211,581,000	158,072,000
Gross Unrealized Gains	4,103,000	7,094,000
Gross Unrealized Losses	2,964,000	124,000
Fair Value	212,720,000	165,042,000
Asset-backed Securities [Member]
Securities available-for-sale: [Abstract]
Amortized Cost	79,318,000	49,598,000
Gross Unrealized Gains	111,000	8,000
Gross Unrealized Losses	849,000	805,000
Fair Value	78,580,000	48,801,000
Corporate Notes [Member]
Securities available-for-sale: [Abstract]
Amortized Cost	8,608,000	9,541,000
Gross Unrealized Gains	39,000	589,000
Gross Unrealized Losses	46,000	17,000
Fair Value	8,601,000	10,113,000
State and Municipal Securities [Member]
Securities held-to-maturity: [Abstract]
Amortized Cost	25,251,316	31,376,840
Gross Unrealized Gains	87,000	257,000
Gross Unrealized Losses	105,000	48,000
Fair Value	25,233,254	31,585,303
Held-to-maturity, Amortized Cost [Abstract]
Amortized Cost	25,251,316	31,376,840
Held-to-maturity, Fair Value [Abstract]
Fair Value	$ 25,233,254	$ 31,585,303