Loans (Impaired Loans Not Covered by Loss Share Agreements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Unpaid Principal Balance
Impaired loans with a related allowance	$ 17,721	$ 17,005
Impaired loans without a related allowance	75,171	69,265
Total impaired loans held to maturity	92,892	86,270
Loan Balance
Impaired loans with a related allowance	17,189	16,995
Impaired loans without a related allowance	69,863	64,801
Total impaired loans held to maturity	87,052	81,796
Impaired loans, related allowance recorded	8,172	7,554
Year-to-Date Avg. Loan Balance
Impaired loans with a related allowance	18,217	15,399
Impaired loans without a related allowance	67,721	66,900
Total impaired loans held to maturity	85,938	82,299
Year-to-Date Interest Income Recognized
Impaired loans with a related allowance	39	101
Impaired loans without a related allowance	1,596	958
Total loans held to maturity	1,635	1,059
Commercial
Unpaid Principal Balance
Impaired loans with a related allowance	13,015	13,267
Impaired loans without a related allowance	32,593	27,194
Total impaired loans held to maturity	45,608	40,461
Loan Balance
Impaired loans with a related allowance	12,998	13,257
Impaired loans without a related allowance	30,092	25,333
Total impaired loans held to maturity	43,090	38,590
Impaired loans, related allowance recorded	6,696	5,951
Year-to-Date Avg. Loan Balance
Impaired loans with a related allowance	13,192	9,162
Impaired loans without a related allowance	29,629	23,052
Total impaired loans held to maturity	42,821	32,214
Year-to-Date Interest Income Recognized
Impaired loans with a related allowance	28	58
Impaired loans without a related allowance	1,211	548
Total loans held to maturity	1,239	606
Commercial | Commercial
Unpaid Principal Balance
Impaired loans with a related allowance	11,696	12,376
Impaired loans without a related allowance	15,180	13,616
Total impaired loans held to maturity	26,876	25,992
Loan Balance
Impaired loans with a related allowance	11,679	12,366
Impaired loans without a related allowance	12,759	11,836
Total impaired loans held to maturity	24,438	24,202
Impaired loans, related allowance recorded	6,245	5,733
Year-to-Date Avg. Loan Balance
Impaired loans with a related allowance	11,757	4,741
Impaired loans without a related allowance	12,831	10,052
Total impaired loans held to maturity	24,588	14,793
Year-to-Date Interest Income Recognized
Impaired loans with a related allowance	6	33
Impaired loans without a related allowance	740	299
Total loans held to maturity	746	332
Commercial | Commercial real estate
Unpaid Principal Balance
Impaired loans with a related allowance	1,319	891
Impaired loans without a related allowance	17,413	13,578
Total impaired loans held to maturity	18,732	14,469
Loan Balance
Impaired loans with a related allowance	1,319	891
Impaired loans without a related allowance	17,333	13,497
Total impaired loans held to maturity	18,652	14,388
Impaired loans, related allowance recorded	451	218
Year-to-Date Avg. Loan Balance
Impaired loans with a related allowance	1,435	4,421
Impaired loans without a related allowance	16,798	13,000
Total impaired loans held to maturity	18,233	17,421
Year-to-Date Interest Income Recognized
Impaired loans with a related allowance	22	25
Impaired loans without a related allowance	471	249
Total loans held to maturity	493	274
Agricultural and agricultural real estate
Unpaid Principal Balance
Impaired loans with a related allowance	2,750	1,718
Impaired loans without a related allowance	23,245	16,836
Total impaired loans held to maturity	25,995	18,554
Loan Balance
Impaired loans with a related allowance	2,237	1,718
Impaired loans without a related allowance	20,449	14,233
Total impaired loans held to maturity	22,686	15,951
Impaired loans, related allowance recorded	916	686
Year-to-Date Avg. Loan Balance
Impaired loans with a related allowance	2,739	2,165
Impaired loans without a related allowance	16,837	14,781
Total impaired loans held to maturity	19,576	16,946
Year-to-Date Interest Income Recognized
Impaired loans with a related allowance	0	2
Impaired loans without a related allowance	60	5
Total loans held to maturity	60	7
Residential real estate
Unpaid Principal Balance
Impaired loans with a related allowance	927	647
Impaired loans without a related allowance	15,824	19,604
Total impaired loans held to maturity	16,751	20,251
Loan Balance
Impaired loans with a related allowance	927	647
Impaired loans without a related allowance	15,813	19,604
Total impaired loans held to maturity	16,740	20,251
Impaired loans, related allowance recorded	110	168
Year-to-Date Avg. Loan Balance
Impaired loans with a related allowance	1,116	1,138
Impaired loans without a related allowance	17,073	23,950
Total impaired loans held to maturity	18,189	25,088
Year-to-Date Interest Income Recognized
Impaired loans with a related allowance	0	12
Impaired loans without a related allowance	280	308
Total loans held to maturity	280	320
Consumer
Unpaid Principal Balance
Impaired loans with a related allowance	1,029	1,373
Impaired loans without a related allowance	3,509	5,631
Total impaired loans held to maturity	4,538	7,004
Loan Balance
Impaired loans with a related allowance	1,027	1,373
Impaired loans without a related allowance	3,509	5,631
Total impaired loans held to maturity	4,536	7,004
Impaired loans, related allowance recorded	450	749
Year-to-Date Avg. Loan Balance
Impaired loans with a related allowance	1,170	2,934
Impaired loans without a related allowance	4,182	5,117
Total impaired loans held to maturity	5,352	8,051
Year-to-Date Interest Income Recognized
Impaired loans with a related allowance	11	29
Impaired loans without a related allowance	45	97
Total loans held to maturity	$ 56	$ 126