LOANS (Loans receivable) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Loans and Leases [Line Items]
Gross loans receivable held to maturity	$ 7,332,862	$ 7,410,881
Unearned discount	(288)	(1,624)
Deferred loan fees	(1,030)	(1,560)
Total net loans receivable held to maturity	7,331,544	7,407,697
Allowance for loan losses	(62,639)	(61,963)
Loans receivable, net	7,268,905	7,345,734
Commercial
Loans and Leases [Line Items]
Gross loans receivable held to maturity	5,745,051	5,731,712
Commercial \| Commercial
Loans and Leases [Line Items]
Gross loans receivable held to maturity	2,042,594	2,020,231
Commercial \| Commercial real estate
Loans and Leases [Line Items]
Gross loans receivable held to maturity	3,702,457	3,711,481
Agricultural and agricultural real estate
Loans and Leases [Line Items]
Gross loans receivable held to maturity	544,805	565,408
Residential real estate
Loans and Leases [Line Items]
Gross loans receivable held to maturity	630,433	673,603
Consumer
Loans and Leases [Line Items]
Gross loans receivable held to maturity	$ 412,573	$ 440,158

Loans and Leases [Line Items]

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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.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Amount before allowance and after 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.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums over and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans and leases covered under loss sharing agreements.

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Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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