FAIR VALUE (Estimated fair value financial instruments incl. carrying amounts) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Securities:
Carried at fair value	$ 3,020,568	$ 2,450,709
Held to maturity	97,905	245,341
Financial liabilities:
Deposits held for sale	0	106,409
Level 1
Financial assets:
Cash and cash equivalents	447,767	273,630
Time deposits in other financial institutions	3,711	4,672
Securities:
Carried at fair value	7,497	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
Derivative assets	0	0
Financial liabilities:
Deposits held for sale	0	0
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	3,013,071	2,425,295
Held to maturity	97,905	245,341
Other investments	29,042	28,396
Loans held for sale	35,427	52,577
Loans, net	7,755,229	7,236,960
Cash surrender value on life insurance	171,471	162,892
Derivative assets	22,152	6,539
Financial liabilities:
Deposits held for sale	0	0
Short term borrowings	107,853	227,010
Other borrowings	278,707	276,966
Derivative liabilities	27,479	6,044
Level 2 \| Interest rate lock commitments
Securities:
Derivative assets	0	0
Level 2 \| Demand deposits
Financial liabilities:
Deposits	3,581,127	3,264,737
Level 2 \| Savings deposits
Financial liabilities:
Deposits	5,770,754	5,107,962
Level 2 \| Time deposits
Financial liabilities:
Deposits	1,117,975	1,023,730
Level 2 \| Forward commitments
Financial liabilities:
Derivative liabilities	209	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	25,078	25,509
Cash surrender value on life insurance	0	0
Derivative assets	0	0
Financial liabilities:
Deposits held for sale	0	100,241
Short term borrowings	0	0
Other borrowings	0	0
Derivative liabilities	0	0
Level 3 \| Interest rate lock commitments
Securities:
Derivative assets	970	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
Level 3 \| Forward commitments
Financial liabilities:
Derivative liabilities	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	2,177,032	1,942,675
Commercial \| Level 2 \| Commercial real estate
Securities:
Loans, net	4,056,599	3,666,733
Commercial \| Level 3 \| Commercial
Securities:
Loans, net	10,767	12,932
Commercial \| Level 3 \| Commercial real estate
Securities:
Loans, net	1,088	405
Agricultural and agricultural real estate \| Level 1
Securities:
Loans, net	0	0
Agricultural and agricultural real estate \| Level 2
Securities:
Loans, net	521,114	542,042
Agricultural and agricultural real estate \| Level 3
Securities:
Loans, net	11,536	11,070
Residential real estate \| Level 1
Securities:
Loans, net	0	0
Residential real estate \| Level 2
Securities:
Loans, net	560,145	654,118
Residential real estate \| Level 3
Securities:
Loans, net	1,042	478
Consumer \| Level 1
Securities:
Loans, net	0	0
Consumer \| Level 2
Securities:
Loans, net	440,339	431,392
Consumer \| Level 3
Securities:
Loans, net	645	624
Carrying Amount
Financial assets:
Cash and cash equivalents	447,767	273,630
Time deposits in other financial institutions	3,711	4,672
Securities:
Carried at fair value	3,020,568	2,450,709
Held to maturity	87,965	236,283
Other investments	29,042	28,396
Loans held for sale	35,427	119,801
Loans, net	7,905,386	7,345,734
Cash surrender value on life insurance	171,471	162,892
Derivative assets	22,152	6,539
Financial liabilities:
Deposits held for sale	0	106,409
Short term borrowings	107,853	227,010
Other borrowings	278,417	274,905
Derivative liabilities	27,479	6,044
Carrying Amount \| Interest rate lock commitments
Securities:
Derivative assets	970	725
Carrying Amount \| Demand deposits
Financial liabilities:
Deposits	3,581,127	3,264,737
Carrying Amount \| Savings deposits
Financial liabilities:
Deposits	5,770,754	5,107,962
Carrying Amount \| Time deposits
Financial liabilities:
Deposits	1,117,975	1,023,730
Carrying Amount \| Forward commitments
Financial liabilities:
Derivative liabilities	209	399
Carrying Amount \| Commercial \| Commercial
Securities:
Loans, net	2,250,134	1,994,785
Carrying Amount \| Commercial \| Commercial real estate
Securities:
Loans, net	4,084,592	3,684,213
Carrying Amount \| Agricultural and agricultural real estate
Securities:
Loans, net	540,406	561,265
Carrying Amount \| Residential real estate
Securities:
Loans, net	587,288	670,473
Carrying Amount \| Consumer
Securities:
Loans, net	442,966	434,998
Estimated Fair Value
Financial assets:
Cash and cash equivalents	447,767	273,630
Time deposits in other financial institutions	3,711	4,672
Securities:
Carried at fair value	3,020,568	2,450,709
Held to maturity	97,905	245,341
Other investments	29,042	28,396
Loans held for sale	35,427	119,801
Loans, net	7,780,307	7,262,469
Cash surrender value on life insurance	171,471	162,892
Derivative assets	22,152	6,539
Financial liabilities:
Deposits held for sale	0	100,241
Short term borrowings	107,853	227,010
Other borrowings	278,707	276,966
Derivative liabilities	27,479	6,044
Estimated Fair Value \| Interest rate lock commitments
Securities:
Derivative assets	970	725
Estimated Fair Value \| Demand deposits
Financial liabilities:
Deposits	3,581,127	3,264,737
Estimated Fair Value \| Savings deposits
Financial liabilities:
Deposits	5,770,754	5,107,962
Estimated Fair Value \| Time deposits
Financial liabilities:
Deposits	1,117,975	1,023,730
Estimated Fair Value \| Forward commitments
Financial liabilities:
Derivative liabilities	209	399
Estimated Fair Value \| Commercial \| Commercial
Securities:
Loans, net	2,187,799	1,955,607
Estimated Fair Value \| Commercial \| Commercial real estate
Securities:
Loans, net	4,057,687	3,667,138
Estimated Fair Value \| Agricultural and agricultural real estate
Securities:
Loans, net	532,650	553,112
Estimated Fair Value \| Residential real estate
Securities:
Loans, net	561,187	654,596
Estimated Fair Value \| Consumer
Securities:
Loans, net	440,984	$ 432,016
Forward commitments \| Level 1
Securities:
Derivative assets	0
Forward commitments \| Level 2
Securities:
Derivative assets	64
Forward commitments \| Level 3
Securities:
Derivative assets	0
Forward commitments \| Carrying Amount
Securities:
Derivative assets	64
Forward commitments \| Estimated Fair Value
Securities:
Derivative assets	$ 64

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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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