Loans and Allowance for Loan Losses (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) alternative	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses, Period Increase (Decrease)	$ 1,081,000	$ 481,000	$ 1,927,000	$ 889,000	$ 1,318,000
Gross loans						$ 1,819,056,000	$ 1,284,677,000
Loans Receivable Held-for-sale, Amount						3,584,000	968,000
loans and leases receivable gross excluding loans held for sale						1,815,472,000	1,283,709,000
Less [Abstract]
Net deferred loan fees, premiums and discounts						12,311,000	2,788,000
Allowance for loan losses	15,164,000	13,931,000	14,576,000	13,682,000	13,682,000	16,161,000	14,576,000	$ 14,228,000
Net loans						1,787,000,000	1,266,345,000
Increase (Decrease) in loans receivable			520,700,000
Impaired Loans [Abstract]
Minimum value of loans individually measured for impairment			$ 250,000
Number of alternatives for measuring impaired loans receivable | alternative			3
Allowance for Loan Losses [Abstract]
Balance, beginning of period	15,164,000	13,931,000	$ 14,576,000	13,682,000	13,682,000
Provision for Loan and Lease Losses	1,081,000	481,000	1,927,000	889,000
Losses charged off	(271,000)	(270,000)	(1,247,000)	(741,000)	(906,000)
Recoveries	187,000	86,000	905,000	398,000	482,000
Balance, end of period	16,161,000	14,228,000	$ 16,161,000	14,228,000	14,576,000
Ending Balance [Abstract]
Individually evaluated for impairment						601,000	134,000	342,000
Collectively evaluated for impairment						15,560,000	14,442,000	13,886,000
Financing Receivable, Allowance for Credit Losses								0
Ending Balance [Abstract]
Individually evaluated for impairment						3,414,000	1,174,000	1,883,000
Collectively evaluated for impairment						1,794,663,000	1,280,715,000	1,234,866,000
Loans Receivable, Net						1,806,745,000	1,281,889,000	1,236,749,000
Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						49,305,000	39,232,000
Agricultural real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						128,954,000	122,579,000
1-4 Family residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						344,190,000	232,351,000
Ending Balance [Abstract]
Period When Loans are Charged-down			180 days
Multifamily residential properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						83,987,000	45,765,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						641,134,000	409,487,000
Loans Receivable Additional Information [Abstract]
Debt coverage ratio			1.20x
Amortization period of loans			twenty years
Commercial real estate | Minimum [Member]
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			65.00%
Commercial real estate | Maximum [Member]
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Loans secured by real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						1,247,570,000	849,414,000
Agricultural loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						81,474,000	75,998,000
Commercial and industrial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						375,824,000	305,851,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Amortization period of loans			seven years
Loans Receivable, Time Period			one year
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses, Period Increase (Decrease)	248,000	305,000	$ 459,000	567,000	633,000
Gross loans						41,313,000	42,097,000
Less [Abstract]
Allowance for loan losses	733,000	382,000	642,000	386,000	386,000	766,000	642,000	654,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	733,000	382,000	642,000	386,000	386,000
Losses charged off	(271,000)	(72,000)	(493,000)	(432,000)	(553,000)
Recoveries	56,000	39,000	158,000	133,000	176,000
Balance, end of period	766,000	654,000	766,000	654,000	642,000
Ending Balance [Abstract]
Individually evaluated for impairment						0	0	194,000
Collectively evaluated for impairment						766,000	642,000	460,000
Ending Balance [Abstract]
Individually evaluated for impairment						20,000	0	224,000
Collectively evaluated for impairment						44,740,000	43,739,000	44,101,000
Loans Receivable, Net						44,760,000	43,739,000	44,325,000
All other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						72,875,000	11,317,000
Agricultural and Farm Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						210,200,000	198,600,000
Less [Abstract]
Increase (Decrease) in loans receivable			$ 11,600,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			65.00%
Amortization period of loans			twenty five years
Loans Receivable, Time Period			one year
Other Grain Farming [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						170,900,000	161,500,000
Less [Abstract]
Increase (Decrease) in loans receivable			$ 9,400,000
Motels and Hotels Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						98,000,000
Non-residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						154,500,000
Residential Buildings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						142,900,000
Automobile Dealers [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans						26,200,000
Unsecured Open-end Loans [Member]
Ending Balance [Abstract]
Period When Loans are Charged-down			180 days
Other Secured Loans [Member]
Ending Balance [Abstract]
Period When Loans are Charged-down			120 days
Commercial/ Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses, Period Increase (Decrease)	445,000	84,000	$ 1,058,000	319,000	451,000
Less [Abstract]
Allowance for loan losses	12,025,000	11,294,000	11,379,000	10,914,000	10,914,000	12,598,000	11,379,000	11,251,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	12,025,000	11,294,000	11,379,000	10,914,000	10,914,000
Losses charged off	0	(174,000)	(582,000)	(245,000)	(289,000)
Recoveries	128,000	47,000	743,000	263,000	303,000
Balance, end of period	12,598,000	11,251,000	12,598,000	11,251,000	11,379,000
Ending Balance [Abstract]
Individually evaluated for impairment						272,000	134,000	148,000
Collectively evaluated for impairment						12,326,000	11,245,000	11,103,000
Ending Balance [Abstract]
Individually evaluated for impairment						1,753,000	744,000	1,248,000
Collectively evaluated for impairment						1,162,399,000	806,992,000	771,140,000
Loans Receivable, Net						1,168,081,000	807,736,000	772,388,000
Agricultural/ Agricultural Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses, Period Increase (Decrease)	476,000	84,000	587,000	35,000	(25,000)
Less [Abstract]
Allowance for loan losses	1,419,000	1,312,000	1,337,000	1,360,000	1,360,000	1,897,000	1,337,000	1,396,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	1,419,000	1,312,000	1,337,000	1,360,000	1,360,000
Losses charged off	0	0	(30,000)	0	0
Recoveries	2,000	0	3,000	1,000	2,000
Balance, end of period	1,897,000	1,396,000	1,897,000	1,396,000	1,337,000
Ending Balance [Abstract]
Individually evaluated for impairment						329,000	0	0
Collectively evaluated for impairment						1,568,000	1,337,000	1,396,000
Ending Balance [Abstract]
Individually evaluated for impairment						1,170,000	430,000	0
Collectively evaluated for impairment						208,775,000	197,636,000	185,275,000
Loans Receivable, Net						209,945,000	198,066,000	185,275,000
Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses, Period Increase (Decrease)	(36,000)	97,000	36,000	77,000	267,000
Less [Abstract]
Allowance for loan losses	924,000	731,000	$ 994,000	790,000	790,000	889,000	994,000	804,000
Loans Receivable Additional Information [Abstract]
Maximum Loan-to-value Ratio (in hundredths)			80.00%
Amortization period of loans			twenty five years
Balloon period			five years
Allowance for Loan Losses [Abstract]
Balance, beginning of period	924,000	731,000	$ 994,000	790,000	790,000
Losses charged off	0	(24,000)	(142,000)	(64,000)	(64,000)
Recoveries	1,000	0	1,000	1,000	1,000
Balance, end of period	889,000	804,000	889,000	804,000	994,000
Ending Balance [Abstract]
Individually evaluated for impairment						0	0	0
Collectively evaluated for impairment						889,000	994,000	804,000
Ending Balance [Abstract]
Individually evaluated for impairment						471,000	0	411,000
Collectively evaluated for impairment						378,749,000	232,348,000	234,350,000
Loans Receivable, Net						383,959,000	232,348,000	234,761,000
Unallocated
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Losses, Period Increase (Decrease)	(52,000)	(89,000)	(213,000)	(109,000)	(8,000)
Less [Abstract]
Allowance for loan losses	63,000	212,000	224,000	232,000	232,000	11,000	224,000	123,000
Allowance for Loan Losses [Abstract]
Balance, beginning of period	63,000	212,000	224,000	232,000	232,000
Losses charged off	0	0	0	0	0
Recoveries	0	0	0	0	0
Balance, end of period	$ 11,000	$ 123,000	$ 11,000	$ 123,000	$ 224,000
Ending Balance [Abstract]
Individually evaluated for impairment						0	0	0
Collectively evaluated for impairment						11,000	224,000	123,000
Ending Balance [Abstract]
Individually evaluated for impairment						0	0	0
Collectively evaluated for impairment						0	0	0
Loans Receivable, Net						0	0	0
Receivables Acquired with Deteriorated Credit Quality [Member]
Less [Abstract]
Net loans						8,668,000	0
Ending Balance [Abstract]
Financing Receivable, Allowance for Credit Losses						0	0	0
Ending Balance [Abstract]
Financing Receivable, Net						8,668,000	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | 1-4 Family residential properties
Ending Balance [Abstract]
Financing Receivable, Net						1,310,000	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Multifamily residential properties
Ending Balance [Abstract]
Financing Receivable, Net						3,430,000	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial and industrial loans
Ending Balance [Abstract]
Financing Receivable, Net						31,000	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer loans
Ending Balance [Abstract]
Financing Receivable, Allowance for Credit Losses						0	0	0
Ending Balance [Abstract]
Financing Receivable, Net						0	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial/ Commercial Real Estate
Ending Balance [Abstract]
Financing Receivable, Allowance for Credit Losses						0	0	0
Ending Balance [Abstract]
Financing Receivable, Net						3,929,000	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Agricultural/ Agricultural Real Estate
Ending Balance [Abstract]
Financing Receivable, Allowance for Credit Losses						0	0	0
Ending Balance [Abstract]
Financing Receivable, Net						0	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Residential Real Estate
Ending Balance [Abstract]
Financing Receivable, Allowance for Credit Losses						0	0	0
Ending Balance [Abstract]
Financing Receivable, Net						4,739,000	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Unallocated
Ending Balance [Abstract]
Financing Receivable, Allowance for Credit Losses						0	0	0
Ending Balance [Abstract]
Financing Receivable, Net						0	$ 0	$ 0
First Clover Leaf [Member]
Less [Abstract]
Net loans						$ 441,100,000