Fair Value (Estimated Fair Value Financial Instruments (Including Carrying Amounts)) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial assets:
Carried at fair value	$ 3,294,361
Held to maturity	100,484	$ 245,341
Financial liabilities:
Deposits held for sale	0	106,409
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and cash equivalents	378,734	273,630
Time deposits in other financial institutions	3,564	4,672
Carried at fair value	8,503	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
Derivatives	0	0
Financial liabilities:
Deposits held for sale		0
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
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	3,304,293	2,425,295
Held to maturity	100,484	245,341
Other investments	31,321	28,396
Loans held for sale	26,748	52,577
Loans, net	8,206,879	7,236,960
Cash surrender value on life insurance	171,625	162,892
Derivatives	17,527	6,539
Financial liabilities:
Deposits held for sale		0
Short term borrowings	182,626	227,010
Other borrowings	278,169	276,966
Derivatives	21,462	6,044
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	15	0
Financial liabilities:
Derivatives	113	399
Significant Other Observable Inputs (Level 2) | Demand deposits
Financial liabilities:
Deposits	3,543,863	3,264,737
Significant Other Observable Inputs (Level 2) | Savings deposits
Financial liabilities:
Deposits	6,307,425	5,107,962
Significant Other Observable Inputs (Level 2) | Time deposits
Financial liabilities:
Deposits	1,193,043	1,023,730
Significant Other Observable Inputs (Level 2) | Commercial | Commercial
Financial assets:
Loans, net	2,327,906	1,942,675
Significant Other Observable Inputs (Level 2) | Commercial | Commercial real estate
Financial assets:
Loans, net	4,328,420	3,666,733
Significant Other Observable Inputs (Level 2) | Agricultural and agricultural real estate
Financial assets:
Loans, net	516,034	542,042
Significant Other Observable Inputs (Level 2) | Residential real estate
Financial assets:
Loans, net	585,094	654,118
Significant Other Observable Inputs (Level 2) | Consumer
Financial assets:
Loans, net	449,425	431,392
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	0
Other investments	0	0
Loans held for sale	0	67,224
Loans, net	36,464	25,509
Cash surrender value on life insurance	0	0
Derivatives	0	0
Financial liabilities:
Deposits held for sale		100,241
Short term borrowings	0	0
Other borrowings	0	0
Derivatives	0	0
Significant Unobservable Inputs (Level 3) | Interest rate lock commitments
Financial assets:
Derivatives	681	725
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
Significant Unobservable Inputs (Level 3) | Commercial | Commercial
Financial assets:
Loans, net	15,173	12,932
Significant Unobservable Inputs (Level 3) | Commercial | Commercial real estate
Financial assets:
Loans, net	4,592	405
Significant Unobservable Inputs (Level 3) | Agricultural and agricultural real estate
Financial assets:
Loans, net	12,623	11,070
Significant Unobservable Inputs (Level 3) | Residential real estate
Financial assets:
Loans, net	3,088	478
Significant Unobservable Inputs (Level 3) | Consumer
Financial assets:
Loans, net	988	624
Carrying Amount
Financial assets:
Cash and cash equivalents	378,734	273,630
Time deposits in other financial institutions	3,564	4,672
Carried at fair value	3,312,796	2,450,709
Held to maturity	91,324	236,283
Other investments	31,321	28,396
Loans held for sale	26,748	119,801
Loans, net	8,297,522	7,345,734
Cash surrender value on life insurance	171,625	162,892
Derivatives	17,527	6,539
Financial liabilities:
Deposits held for sale		106,409
Short term borrowings	182,626	227,010
Other borrowings	275,773	274,905
Derivatives	21,462	6,044
Carrying Amount | Interest rate lock commitments
Financial assets:
Derivatives	681	725
Carrying Amount | Forward commitments
Financial assets:
Derivatives	0	0
Financial liabilities:
Derivatives	113	399
Carrying Amount | Demand deposits
Financial liabilities:
Deposits	3,543,863	3,264,737
Carrying Amount | Savings deposits
Financial liabilities:
Deposits	6,307,425	5,107,962
Carrying Amount | Time deposits
Financial liabilities:
Deposits	1,193,043	1,023,730
Deposits held for sale		106,400
Carrying Amount | Commercial | Commercial
Financial assets:
Loans, net	2,390,254	1,994,785
Carrying Amount | Commercial | Commercial real estate
Financial assets:
Loans, net	4,336,355	3,684,213
Carrying Amount | Agricultural and agricultural real estate
Financial assets:
Loans, net	528,195	561,265
Carrying Amount | Residential real estate
Financial assets:
Loans, net	595,331	670,473
Carrying Amount | Consumer
Financial assets:
Loans, net	447,387	434,998
Estimated Fair Value
Financial assets:
Cash and cash equivalents	378,734	273,630
Time deposits in other financial institutions	3,564	4,672
Carried at fair value	3,312,796	2,450,709
Held to maturity	100,484	245,341
Other investments	31,321	28,396
Loans held for sale	26,748	119,801
Loans, net	8,243,343	7,262,469
Cash surrender value on life insurance	171,625	162,892
Derivatives	17,527	6,539
Financial liabilities:
Deposits held for sale		100,241
Short term borrowings	182,626	227,010
Other borrowings	278,169	276,966
Derivatives	21,462	6,044
Estimated Fair Value | Interest rate lock commitments
Financial assets:
Derivatives	681	725
Estimated Fair Value | Forward commitments
Financial assets:
Derivatives	15	0
Financial liabilities:
Derivatives	113	399
Estimated Fair Value | Demand deposits
Financial liabilities:
Deposits	3,543,863	3,264,737
Estimated Fair Value | Savings deposits
Financial liabilities:
Deposits	6,307,425	5,107,962
Estimated Fair Value | Time deposits
Financial liabilities:
Deposits	1,193,043	1,023,730
Estimated Fair Value | Commercial | Commercial
Financial assets:
Loans, net	2,343,079	1,955,607
Estimated Fair Value | Commercial | Commercial real estate
Financial assets:
Loans, net	4,333,012	3,667,138
Estimated Fair Value | Agricultural and agricultural real estate
Financial assets:
Loans, net	528,657	553,112
Estimated Fair Value | Residential real estate
Financial assets:
Loans, net	588,182	654,596
Estimated Fair Value | Consumer
Financial assets:
Loans, net	$ 450,413	$ 432,016