Fair Value (Estimated Fair Value Financial Instruments (Including Carrying Amounts)) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financial assets:
Carried at fair value		$ 2,216,753
Held to maturity	$ 245,341	265,494
Financial liabilities:
Deposits held for sale	106,409	0
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	273,630	196,003
Time deposits in other financial institutions	4,672	9,820
Carried at fair value	25,414	3,484
Held to maturity	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	0	0
Cash surrender value on life insurance	0	0
Derivatives	0	0
Financial liabilities:
Short term borrowings	0	0
Other borrowings	0	0
Derivatives	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Interest rate lock commitments
Financial assets:
Derivatives	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Forward commitments
Financial assets:
Derivatives	0	0
Financial liabilities:
Derivatives	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Demand deposits
Financial liabilities:
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Savings deposits
Financial liabilities:
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Time deposits
Financial liabilities:
Deposits	0	0
Deposits held for sale	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Commercial \| Commercial
Financial assets:
Loans, net	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Commercial \| Commercial real estate
Financial assets:
Loans, net	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Agricultural and agricultural real estate
Financial assets:
Loans, net	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Residential real estate
Financial assets:
Loans, net	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Consumer
Financial assets:
Loans, net	0	0
Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0	0
Carried at fair value	2,425,295	2,213,269
Held to maturity	245,341	265,494
Other investments	28,396	22,563
Loans held for sale	52,577	44,560
Loans, net	7,236,960	6,291,503
Cash surrender value on life insurance	162,892	142,818
Derivatives	6,539	3,933
Financial liabilities:
Short term borrowings	227,010	324,691
Other borrowings	276,966	285,609
Derivatives	6,044	5,167
Significant Other Observable Inputs (Level 2) \| Interest rate lock commitments
Financial assets:
Derivatives	0	0
Significant Other Observable Inputs (Level 2) \| Forward commitments
Financial assets:
Derivatives	0	80
Financial liabilities:
Derivatives	399	232
Significant Other Observable Inputs (Level 2) \| Demand deposits
Financial liabilities:
Deposits	3,264,737	2,983,128
Significant Other Observable Inputs (Level 2) \| Savings deposits
Financial liabilities:
Deposits	5,107,962	4,240,328
Significant Other Observable Inputs (Level 2) \| Time deposits
Financial liabilities:
Deposits	1,023,730	923,453
Deposits held for sale	0
Significant Other Observable Inputs (Level 2) \| Commercial \| Commercial
Financial assets:
Loans, net	1,942,675	1,614,744
Significant Other Observable Inputs (Level 2) \| Commercial \| Commercial real estate
Financial assets:
Loans, net	3,666,733	3,123,062
Significant Other Observable Inputs (Level 2) \| Agricultural and agricultural real estate
Financial assets:
Loans, net	542,042	500,581
Significant Other Observable Inputs (Level 2) \| Residential real estate
Financial assets:
Loans, net	654,118	613,530
Significant Other Observable Inputs (Level 2) \| Consumer
Financial assets:
Loans, net	431,392	439,586
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0	0
Carried at fair value	0	0
Held to maturity	0
Other investments	0	0
Loans held for sale	67,224	0
Loans, net	25,509	23,469
Cash surrender value on life insurance	0	0
Derivatives	0	0
Financial liabilities:
Short term borrowings	0	0
Other borrowings	0	0
Derivatives	0	0
Significant Unobservable Inputs (Level 3) \| Interest rate lock commitments
Financial assets:
Derivatives	725	1,738
Significant Unobservable Inputs (Level 3) \| Forward commitments
Financial assets:
Derivatives	0	0
Financial liabilities:
Derivatives	0	0
Significant Unobservable Inputs (Level 3) \| Demand deposits
Financial liabilities:
Deposits	0	0
Significant Unobservable Inputs (Level 3) \| Savings deposits
Financial liabilities:
Deposits	0	0
Significant Unobservable Inputs (Level 3) \| Time deposits
Financial liabilities:
Deposits	0	0
Deposits held for sale	100,241
Significant Unobservable Inputs (Level 3) \| Commercial \| Commercial
Financial assets:
Loans, net	12,932	3,212
Significant Unobservable Inputs (Level 3) \| Commercial \| Commercial real estate
Financial assets:
Loans, net	405	9,480
Significant Unobservable Inputs (Level 3) \| Agricultural and agricultural real estate
Financial assets:
Loans, net	11,070	8,406
Significant Unobservable Inputs (Level 3) \| Residential real estate
Financial assets:
Loans, net	478	1,137
Significant Unobservable Inputs (Level 3) \| Consumer
Financial assets:
Loans, net	624	1,234
Carrying Amount
Financial assets:
Cash and cash equivalents	273,630	196,003
Time deposits in other financial institutions	4,672	9,820
Carried at fair value	2,450,709	2,216,753
Held to maturity	236,283	253,550
Other investments	28,396	22,563
Loans held for sale	119,801	44,560
Loans, net	7,345,734	6,335,778
Cash surrender value on life insurance	162,892	142,818
Derivatives	6,539	3,933
Financial liabilities:
Short term borrowings	227,010	324,691
Other borrowings	274,905	285,011
Derivatives	6,044	5,167
Carrying Amount \| Interest rate lock commitments
Financial assets:
Derivatives	725	1,738
Carrying Amount \| Forward commitments
Financial assets:
Derivatives	0	80
Financial liabilities:
Derivatives	399	232
Carrying Amount \| Demand deposits
Financial liabilities:
Deposits	3,264,737	2,983,128
Carrying Amount \| Savings deposits
Financial liabilities:
Deposits	5,107,962	4,240,328
Carrying Amount \| Time deposits
Financial liabilities:
Deposits	1,023,730	923,453
Deposits held for sale	106,409
Carrying Amount \| Commercial \| Commercial
Financial assets:
Loans, net	1,994,785	1,628,043
Carrying Amount \| Commercial \| Commercial real estate
Financial assets:
Loans, net	3,684,213	3,140,427
Carrying Amount \| Agricultural and agricultural real estate
Financial assets:
Loans, net	561,265	508,075
Carrying Amount \| Residential real estate
Financial assets:
Loans, net	670,473	620,939
Carrying Amount \| Consumer
Financial assets:
Loans, net	434,998	438,294
Estimated Fair Value
Financial assets:
Cash and cash equivalents	273,630	196,003
Time deposits in other financial institutions	4,672	9,820
Carried at fair value	2,450,709	2,216,753
Held to maturity	245,341	265,494
Other investments	28,396	22,563
Loans held for sale	119,801	44,560
Loans, net	7,262,469	6,314,972
Cash surrender value on life insurance	162,892	142,818
Derivatives	6,539	3,933
Financial liabilities:
Short term borrowings	227,010	324,691
Other borrowings	276,966	285,609
Derivatives	6,044	5,167
Estimated Fair Value \| Interest rate lock commitments
Financial assets:
Derivatives	725	1,738
Estimated Fair Value \| Forward commitments
Financial assets:
Derivatives	0	80
Financial liabilities:
Derivatives	399	232
Estimated Fair Value \| Demand deposits
Financial liabilities:
Deposits	3,264,737	2,983,128
Estimated Fair Value \| Savings deposits
Financial liabilities:
Deposits	5,107,962	4,240,328
Estimated Fair Value \| Time deposits
Financial liabilities:
Deposits	1,023,730	923,453
Deposits held for sale	100,241
Estimated Fair Value \| Commercial \| Commercial
Financial assets:
Loans, net	1,955,607	1,617,956
Estimated Fair Value \| Commercial \| Commercial real estate
Financial assets:
Loans, net	3,667,138	3,132,542
Estimated Fair Value \| Agricultural and agricultural real estate
Financial assets:
Loans, net	553,112	508,987
Estimated Fair Value \| Residential real estate
Financial assets:
Loans, net	654,596	614,667
Estimated Fair Value \| Consumer
Financial assets:
Loans, net	$ 432,016	$ 440,820

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Other Borrowings, Fair Value Disclosure

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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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 of investment in debt security measured at amortized cost (held-to-maturity).

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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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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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