FAIR VALUE (Estimated fair value financial instruments incl. carrying amounts) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Securities:
Carried at fair value	$ 2,561,887	$ 2,450,709
Held to maturity	96,619	245,341
Financial liabilities:
Deposits held for sale	0	106,409
Level 1
Financial assets:
Cash and cash equivalents	642,139	273,630
Time deposits in other financial institutions	4,430	4,672
Securities:
Carried at fair value	12,480	25,414
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
Interest rate lock commitments	0	0
Financial liabilities:
Short term borrowings	0	0
Other borrowings	0	0
Fair Value	0	0
Level 1 \| Interest rate lock commitments
Securities:
Interest rate lock commitments	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
Deposits held for sale	0	0
Level 1 \| Forward commitments
Financial liabilities:
Fair Value	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	2,549,407	2,425,295
Held to maturity	96,619	245,341
Other investments	31,366	28,396
Loans held for sale	34,575	52,577
Loans, net	7,697,443	7,236,960
Cash surrender value on life insurance	170,421	162,892
Interest rate lock commitments	14,413	6,539
Financial liabilities:
Short term borrowings	107,260	227,010
Other borrowings	283,695	276,966
Fair Value	19,383	6,044
Level 2 \| Interest rate lock commitments
Securities:
Interest rate lock commitments	0	0
Level 2 \| Demand deposits
Financial liabilities:
Deposits	3,426,758	3,264,737
Level 2 \| Savings deposits
Financial liabilities:
Deposits	5,533,503	5,107,962
Level 2 \| Time deposits
Financial liabilities:
Deposits	1,148,296	1,023,730
Deposits held for sale	0	0
Level 2 \| Forward commitments
Financial liabilities:
Fair Value	430	399
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	67,224
Loans, net	24,880	25,509
Cash surrender value on life insurance	0	0
Interest rate lock commitments	0	0
Financial liabilities:
Short term borrowings	0	0
Other borrowings	0	0
Fair Value	0	0
Level 3 \| Interest rate lock commitments
Securities:
Interest rate lock commitments	1,072	725
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
Deposits held for sale	0	100,241
Level 3 \| Forward commitments
Financial liabilities:
Fair Value	0	0
Commercial \| Level 1 \| Commercial
Securities:
Loans, net	0	0
Commercial \| Level 1 \| Commercial real estate
Securities:
Loans, net	0	0
Commercial \| Level 2 \| Commercial
Securities:
Loans, net	2,171,693	1,942,675
Commercial \| Level 2 \| Commercial real estate
Securities:
Loans, net	3,947,466	3,666,733
Commercial \| Level 3 \| Commercial
Securities:
Loans, net	13,337	12,932
Commercial \| Level 3 \| Commercial real estate
Securities:
Loans, net	808	405
Agricultural and agricultural real estate \| Level 1
Securities:
Loans, net	0	0
Agricultural and agricultural real estate \| Level 2
Securities:
Loans, net	526,894	542,042
Agricultural and agricultural real estate \| Level 3
Securities:
Loans, net	9,032	11,070
Residential real estate \| Level 1
Securities:
Loans, net	0	0
Residential real estate \| Level 2
Securities:
Loans, net	596,458	654,118
Residential real estate \| Level 3
Securities:
Loans, net	1,076	478
Consumer \| Level 1
Securities:
Loans, net	0	0
Consumer \| Level 2
Securities:
Loans, net	454,932	431,392
Consumer \| Level 3
Securities:
Loans, net	627	624
Carrying Amount
Financial assets:
Cash and cash equivalents	642,139	273,630
Time deposits in other financial institutions	4,430	4,672
Securities:
Carried at fair value	2,561,887	2,450,709
Held to maturity	88,166	236,283
Other investments	31,366	28,396
Loans held for sale	34,575	119,801
Loans, net	7,789,201	7,345,734
Cash surrender value on life insurance	170,421	162,892
Interest rate lock commitments	14,413	6,539
Financial liabilities:
Short term borrowings	107,260	227,010
Other borrowings	282,863	274,905
Fair Value	19,383	6,044
Carrying Amount \| Interest rate lock commitments
Securities:
Interest rate lock commitments	1,072	725
Carrying Amount \| Demand deposits
Financial liabilities:
Deposits	3,426,758	3,264,737
Carrying Amount \| Savings deposits
Financial liabilities:
Deposits	5,533,503	5,107,962
Carrying Amount \| Time deposits
Financial liabilities:
Deposits	1,148,296	1,023,730
Deposits held for sale	0	106,409
Carrying Amount \| Forward commitments
Financial liabilities:
Fair Value	430	399
Carrying Amount \| Commercial \| Commercial
Securities:
Loans, net	2,213,691	1,994,785
Carrying Amount \| Commercial \| Commercial real estate
Securities:
Loans, net	3,963,406	3,684,213
Carrying Amount \| Agricultural and agricultural real estate
Securities:
Loans, net	544,109	561,265
Carrying Amount \| Residential real estate
Securities:
Loans, net	611,025	670,473
Carrying Amount \| Consumer
Securities:
Loans, net	456,970	434,998
Estimated Fair Value
Financial assets:
Cash and cash equivalents	642,139	273,630
Time deposits in other financial institutions	4,430	4,672
Securities:
Carried at fair value	2,561,887	2,450,709
Held to maturity	96,619	245,341
Other investments	31,366	28,396
Loans held for sale	34,575	119,801
Loans, net	7,722,323	7,262,469
Cash surrender value on life insurance	170,421	162,892
Interest rate lock commitments	14,413	6,539
Financial liabilities:
Short term borrowings	107,260	227,010
Other borrowings	283,695	276,966
Fair Value	19,383	6,044
Estimated Fair Value \| Interest rate lock commitments
Securities:
Interest rate lock commitments	1,072	725
Estimated Fair Value \| Demand deposits
Financial liabilities:
Deposits	3,426,758	3,264,737
Estimated Fair Value \| Savings deposits
Financial liabilities:
Deposits	5,533,503	5,107,962
Estimated Fair Value \| Time deposits
Financial liabilities:
Deposits	1,148,296	1,023,730
Deposits held for sale	0	100,241
Estimated Fair Value \| Forward commitments
Financial liabilities:
Fair Value	430	399
Estimated Fair Value \| Commercial \| Commercial
Securities:
Loans, net	2,185,030	1,955,607
Estimated Fair Value \| Commercial \| Commercial real estate
Securities:
Loans, net	3,948,274	3,667,138
Estimated Fair Value \| Agricultural and agricultural real estate
Securities:
Loans, net	535,926	553,112
Estimated Fair Value \| Residential real estate
Securities:
Loans, net	597,534	654,596
Estimated Fair Value \| Consumer
Securities:
Loans, net	455,559	$ 432,016
Forward commitments \| Level 1
Securities:
Interest rate lock commitments	0
Forward commitments \| Level 2
Securities:
Interest rate lock commitments	2
Forward commitments \| Level 3
Securities:
Interest rate lock commitments	0
Forward commitments \| Carrying Amount
Securities:
Interest rate lock commitments	2
Forward commitments \| Estimated Fair Value
Securities:
Interest rate lock commitments	$ 2

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Other Borrowings, Fair Value Disclosure

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value portion of the amount that could be realized under a life insurance contract or contracts owned by the entity, commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI).

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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