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FAIR VALUE DISCLOSURES - Certain assets measured on a non recurring basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Loan Impairment Assessment
Risk rating	$ 2,640,393	$ 2,613,805
Financing Receivable, Allowance for Credit Losses	31,194	25,280	$ 24,643	$ 23,693
Total loans	2,678,411	2,646,673
Commercial and industrial
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses	9,535	7,671	8,416	7,719
Total loans	542,650	527,607
Commercial real estate
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses	9,576	7,975	6,784	6,730
Total loans	904,395	900,746
1-4 family residential
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses	2,430	2,257	2,249	2,281
Total loans	276,142	280,192
Consumer
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses	477	388	357	387
Total loans	38,133	36,782
Agriculture
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses	129	74	50	62
Total loans	7,520	9,812
Other
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses	839	770	630	$ 705
Total loans	84,076	86,513
Level 3 Inputs \| Non-recurring basis
Loan Impairment Assessment
Recorded Investment	13,498	11,303
Specific ACL	409	437
Net	13,089	10,866
Level 3 Inputs \| Non-recurring basis \| Commercial and industrial
Loan Impairment Assessment
Recorded Investment	1,528	999
Specific ACL	409	416
Net	1,119	583
Level 3 Inputs \| Non-recurring basis \| 1-4 family residential
Loan Impairment Assessment
Recorded Investment	3,703	3,651
Specific ACL		15
Net	3,703	3,636
Level 3 Inputs \| Non-recurring basis \| Other
Loan Impairment Assessment
Recorded Investment	8,267	6,653
Specific ACL		6
Net	8,267	$ 6,647
Specific reserve
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses	409		788
Specific reserve \| Commercial and industrial
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses	$ 409		582
Specific reserve \| Commercial real estate
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses			33
Specific reserve \| 1-4 family residential
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses			77
Specific reserve \| Other
Loan Impairment Assessment
Financing Receivable, Allowance for Credit Losses			$ 96