FAIR VALUE (Estimated fair value financial instruments incl. carrying amounts) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Securities:
Held to maturity	$ 95,082	$ 100,041
Level 1
Financial assets:
Cash and cash equivalents	467,862	337,903
Time deposits in other financial institutions	3,138	3,129
Securities:
Carried at fair value	1,019	2,026
Held to maturity	0	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	0	0
Cash surrender value on life insurance	0	0
Derivative assets	0	0
Financial liabilities:
Short term borrowings	0	0
Other borrowings	0	0
Derivative liabilities	0	0
Level 1 \| Interest rate lock commitments
Securities:
Derivative assets	0	0
Level 1 \| Demand deposits
Financial liabilities:
Deposits	0	0
Level 1 \| Savings deposits
Financial liabilities:
Deposits	0	0
Level 1 \| Time deposits
Financial liabilities:
Deposits	0	0
Level 1 \| Forward commitments
Financial liabilities:
Derivative liabilities	0	0
Level 2
Financial assets:
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0	0
Securities:
Carried at fair value	6,369,476	6,125,949
Held to maturity	95,082	100,041
Other investments	74,935	75,523
Loans held for sale	43,037	57,949
Loans, net	9,852,310	9,735,181
Cash surrender value on life insurance	188,521	187,664
Derivative assets	23,991	44,102
Financial liabilities:
Short term borrowings	140,597	167,872
Other borrowings	350,964	458,806
Derivative liabilities	29,791	51,962
Level 2 \| Interest rate lock commitments
Securities:
Derivative assets	0	0
Level 2 \| Demand deposits
Financial liabilities:
Deposits	6,175,946	5,688,810
Level 2 \| Savings deposits
Financial liabilities:
Deposits	819,251	8,019,704
Level 2 \| Time deposits
Financial liabilities:
Deposits	1,203,854	1,273,468
Level 2 \| Forward commitments
Financial liabilities:
Derivative liabilities	4	697
Level 3
Financial assets:
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0	0
Securities:
Carried at fair value	0	0
Held to maturity	0	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	31,175	34,488
Cash surrender value on life insurance	0	0
Derivative assets	0	0
Financial liabilities:
Short term borrowings	0	0
Other borrowings	0	0
Derivative liabilities	0	0
Level 3 \| Interest rate lock commitments
Securities:
Derivative assets	1,857	1,827
Level 3 \| Demand deposits
Financial liabilities:
Deposits	0	0
Level 3 \| Savings deposits
Financial liabilities:
Deposits	0	0
Level 3 \| Time deposits
Financial liabilities:
Deposits	0	0
Level 3 \| Forward commitments
Financial liabilities:
Derivative liabilities	0	0
Commercial and industrial \| Level 1 \| Commercial and industrial
Securities:
Loans, net	0	0
Commercial and industrial \| Level 1 \| Real estate construction
Securities:
Loans, net	0	0
Commercial and industrial \| Level 2 \| Commercial and industrial
Securities:
Loans, net	2,358,274	2,379,785
Commercial and industrial \| Level 2 \| Real estate construction
Securities:
Loans, net	782,155	849,224
Commercial and industrial \| Level 3 \| Commercial and industrial
Securities:
Loans, net	10,621	11,256
Commercial and industrial \| Level 3 \| Real estate construction
Securities:
Loans, net	0	0
Paycheck Protection Program ("PPP") \| Level 1 \| Commercial and industrial
Securities:
Loans, net	0	0
Paycheck Protection Program ("PPP") \| Level 2 \| Commercial and industrial
Securities:
Loans, net	1,155,328	957,785
Paycheck Protection Program ("PPP") \| Level 3 \| Commercial and industrial
Securities:
Loans, net	0	0
Owner occupied commercial real estate \| Level 1 \| Commercial and industrial
Securities:
Loans, net	0	0
Owner occupied commercial real estate \| Level 2 \| Commercial and industrial
Securities:
Loans, net	1,802,788	1,739,523
Owner occupied commercial real estate \| Level 3 \| Commercial and industrial
Securities:
Loans, net	1,233	5,874
Non-owner occupied commercial real estate \| Level 1 \| Commercial and industrial
Securities:
Loans, net	0	0
Non-owner occupied commercial real estate \| Level 2 \| Commercial and industrial
Securities:
Loans, net	1,921,571	1,887,306
Non-owner occupied commercial real estate \| Level 3 \| Commercial and industrial
Securities:
Loans, net	12,050	4,907
Agricultural and agricultural real estate \| Level 1
Securities:
Loans, net	0	0
Agricultural and agricultural real estate \| Level 2
Securities:
Loans, net	662,443	685,278
Agricultural and agricultural real estate \| Level 3
Securities:
Loans, net	7,271	12,451
Residential real estate \| Level 1
Securities:
Loans, net	0	0
Residential real estate \| Level 2
Securities:
Loans, net	775,020	828,366
Residential real estate \| Level 3
Securities:
Loans, net	0	0
Consumer \| Level 1
Securities:
Loans, net	0	0
Consumer \| Level 2
Securities:
Loans, net	394,731	407,914
Consumer \| Level 3
Securities:
Loans, net	0	0
Carrying Amount
Financial assets:
Cash and cash equivalents	467,862	337,903
Time deposits in other financial institutions	3,138	3,129
Securities:
Carried at fair value	6,370,495	6,127,975
Held to maturity	85,293	88,839
Other investments	74,935	75,253
Loans held for sale	43,037	57,949
Loans, net	9,920,284	9,891,445
Cash surrender value on life insurance	188,521	187,664
Derivative assets	23,991	44,102
Financial liabilities:
Short term borrowings	140,597	167,872
Other borrowings	349,514	457,042
Derivative liabilities	29,791	51,962
Carrying Amount \| Interest rate lock commitments
Securities:
Derivative assets	1,857	1,827
Carrying Amount \| Demand deposits
Financial liabilities:
Deposits	6,175,946	5,688,810
Carrying Amount \| Savings deposits
Financial liabilities:
Deposits	8,179,251	8,019,704
Carrying Amount \| Time deposits
Financial liabilities:
Deposits	1,203,854	1,271,391
Carrying Amount \| Forward commitments
Financial liabilities:
Derivative liabilities	4	697
Carrying Amount \| Commercial and industrial \| Commercial and industrial
Securities:
Loans, net	2,385,165	2,495,981
Carrying Amount \| Commercial and industrial \| Real estate construction
Securities:
Loans, net	776,096	843,140
Carrying Amount \| Paycheck Protection Program ("PPP") \| Commercial and industrial
Securities:
Loans, net	1,155,328	957,785
Carrying Amount \| Owner occupied commercial real estate \| Commercial and industrial
Securities:
Loans, net	1,818,143	1,756,405
Carrying Amount \| Non-owner occupied commercial real estate \| Commercial and industrial
Securities:
Loans, net	1,942,489	1,900,608
Carrying Amount \| Agricultural and agricultural real estate
Securities:
Loans, net	676,858	707,397
Carrying Amount \| Residential real estate
Securities:
Loans, net	775,982	828,507
Carrying Amount \| Consumer
Securities:
Loans, net	390,223	401,622
Estimated Fair Value
Financial assets:
Cash and cash equivalents	467,862	337,903
Time deposits in other financial institutions	3,138	3,129
Securities:
Carried at fair value	6,370,495	6,127,975
Held to maturity	95,082	100,041
Other investments	74,935	75,523
Loans held for sale	43,037	57,949
Loans, net	9,883,485	9,769,669
Cash surrender value on life insurance	188,521	187,664
Derivative assets	23,991	44,102
Financial liabilities:
Short term borrowings	140,597	167,872
Other borrowings	350,964	458,806
Derivative liabilities	29,791	51,962
Estimated Fair Value \| Interest rate lock commitments
Securities:
Derivative assets	1,857	1,827
Estimated Fair Value \| Demand deposits
Financial liabilities:
Deposits	6,175,946	5,688,810
Estimated Fair Value \| Savings deposits
Financial liabilities:
Deposits	819,251	8,019,704
Estimated Fair Value \| Time deposits
Financial liabilities:
Deposits	1,203,854	1,273,468
Estimated Fair Value \| Forward commitments
Financial liabilities:
Derivative liabilities	4	697
Estimated Fair Value \| Commercial and industrial \| Commercial and industrial
Securities:
Loans, net	2,368,895	2,391,041
Estimated Fair Value \| Commercial and industrial \| Real estate construction
Securities:
Loans, net	782,155	849,224
Estimated Fair Value \| Paycheck Protection Program ("PPP") \| Commercial and industrial
Securities:
Loans, net	1,155,328	957,785
Estimated Fair Value \| Owner occupied commercial real estate \| Commercial and industrial
Securities:
Loans, net	1,804,021	1,745,397
Estimated Fair Value \| Non-owner occupied commercial real estate \| Commercial and industrial
Securities:
Loans, net	1,933,621	1,892,213
Estimated Fair Value \| Agricultural and agricultural real estate
Securities:
Loans, net	669,714	697,729
Estimated Fair Value \| Residential real estate
Securities:
Loans, net	775,020	828,366
Estimated Fair Value \| Consumer
Securities:
Loans, net	394,731	$ 407,914
Forward commitments \| Level 1
Securities:
Derivative assets	0
Forward commitments \| Level 2
Securities:
Derivative assets	1,213
Forward commitments \| Level 3
Securities:
Derivative assets	0
Forward commitments \| Carrying Amount
Securities:
Derivative assets	1,213
Forward commitments \| Estimated Fair Value
Securities:
Derivative assets	$ 1,213

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