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Amount of first loss position maintained by Federal Home Loan Bank under Mortgage Partnership Finance Program.

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The balance of financing receivables that were acquired with deteriorated credit quality.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements, related to Individually evaluated for impairment, related to Collectively evaluated for impairment.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale. Related to Collectively evaluated for impairment.

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Refers to Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale. Related to Individually evaluated for impairment.

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The number of days past due before a loan is classified as impaired.

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Real estate loans serviced for Freddie Mac and Fannie Mae, which are not included in the consolidated balance sheet.

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Real estate loans sold to Freddie Mac and Fannie Mae without recourse which are not included in the consolidated balance sheet.

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The amount of the loan's contractually required payments receivable in excess of the amount of its cash flows expected to be collected. This relates to loans with deteriorating of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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Amount of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

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Fair value at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

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LOANS AND RELATED ALLOWANCE FOR LOAN LOSSES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 11, 2015
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			$ 1,000,525	$ 799,611
Individually evaluated for impairment			24,398	17,693
Loans acquired with deteriorated credit quality			2,638	3,367
Collectively evaluated for impairment			973,489	778,551
Allowance for loan losses			11,190	8,886
Allowance for loan losses related to individually evaluated for impairment			410	487
Allowance for loan losses related to loans acquired with deteriorated credit quality			0	0
Allowance for loan losses related to collectively evaluated for impairment			10,780	8,399
Net loans			989,335	790,725
Net loans, individually evaluated for impairment			23,988	17,206
Net loans, loans acquired with deteriorated credit quality			2,638	3,367
Net loans, collectively evaluated for impairment			962,709	770,152
Net unamortized loan fees and costs			794	732
Real estate loans serviced for Freddie Mac and Fannie Mae			142,972	135,404
Real estate loans sold to Freddie Mac and Fannie Mae without recourse	$ 114,643	$ 102,444
Portfolio balance under MPF			28,329	32,960
First-loss position for MPF maintained by FHLB			123
Credit enhancement for MPF by FHLB	$ 980
Number of days past for loan to be considered impaired, Minimum	90 days
Minimum [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Number of days past for loan to be considered impaired, Minimum	90 days
First Mortgage [Member] \| Minimum [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Period of mortgage on real estate	15 years
First Mortgage [Member] \| Maximum [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Period of mortgage on real estate	30 years
Second Mortgage [Member] \| Maximum [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Period of mortgage on real estate	15 years
Real Estate Loans [Member] \| Residential [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			214,479	207,423
Individually evaluated for impairment			1,065	957
Loans acquired with deteriorated credit quality			33	35
Collectively evaluated for impairment			213,381	206,431
Real Estate Loans [Member] \| Commercial [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			308,084	252,577
Individually evaluated for impairment			13,864	5,742
Loans acquired with deteriorated credit quality			1,460	1,969
Collectively evaluated for impairment			292,760	244,866
Real Estate Loans [Member] \| Agricultural [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			239,957	123,624
Individually evaluated for impairment			3,901	3,347
Loans acquired with deteriorated credit quality			702	738
Collectively evaluated for impairment			235,354	119,539
Real Estate Loans [Member] \| Construction [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			13,502	25,441
Individually evaluated for impairment			0	0
Loans acquired with deteriorated credit quality			0	0
Collectively evaluated for impairment			13,502	25,441
Consumer [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			9,944	11,005
Individually evaluated for impairment			8	0
Loans acquired with deteriorated credit quality			0	4
Collectively evaluated for impairment			9,936	11,001
Other Commercial Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			72,013	58,639
Individually evaluated for impairment			4,197	5,994
Loans acquired with deteriorated credit quality			443	621
Collectively evaluated for impairment			67,373	52,024
Other Agricultural Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			37,809	23,388
Individually evaluated for impairment			1,363	1,653
Loans acquired with deteriorated credit quality			0	0
Collectively evaluated for impairment			36,446	21,735
State and Political Subdivision Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			104,737	97,514
Individually evaluated for impairment			0	0
Loans acquired with deteriorated credit quality			0	0
Collectively evaluated for impairment			104,737	97,514
First National Bank of Fredericksburg [Member]
Components of the purchase accounting adjustments related to the purchased impaired loans in FNB Acquisition [Abstract]
Estimated fair value					$ 3,809
Contractually required principal and interest at acquisition					9,913
Expected cash flows					4,474
Non-accretable discount					5,439
Accretable discount	$ 389	389	106	389	665
Changes in the accretable yield for purchased credit-impaired loans [Roll Forward]
Balance at beginning of period	389	637
Accretion	(632)	(349)
Reclassification of non-accretable discount	349	101
Balance at end of period	$ 106	$ 389
Loans acquired with specific evidence of deterioration in credit quality [Abstract]
Outstanding balance			5,295	6,487	$ 6,969
Carrying amount			$ 2,638	$ 3,367