Loans (Risk Category of Loans by Class) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 3,225,232		$ 3,081,973
Commercial and Industrial Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	388,453
2019	96,358
2018	56,548
2017	40,874
2016	25,295
Prior	63,511
Revolving Loans Amortized Cost Basis	110,508
Total	781,547	$ 534,692	589,758
Commercial Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	195,605
2019	246,047
2018	208,004
2017	220,961
2016	193,319
Prior	353,692
Revolving Loans Amortized Cost Basis	35,652
Total	1,453,280	1,500,247	1,495,862
Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	42,877
2019	36,244
2018	37,021
2017	44,271
2016	30,661
Prior	91,847
Revolving Loans Amortized Cost Basis	93,294
Total	376,215	384,654	384,526
Leases
Financing Receivable, Credit Quality Indicator [Line Items]
2020	14,950
2019	19,334
2018	10,342
2017	6,297
2016	2,194
Prior	4,358
Revolving Loans Amortized Cost Basis	0
Total	57,475	$ 57,257
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Total			2,336,007
Pass | Commercial and Industrial Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	387,099
2019	95,812
2018	54,005
2017	37,396
2016	24,134
Prior	55,538
Revolving Loans Amortized Cost Basis	100,294
Total	754,278
Pass | Commercial Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	195,078
2019	241,890
2018	204,211
2017	214,673
2016	186,951
Prior	328,350
Revolving Loans Amortized Cost Basis	35,405
Total	1,406,558		1,453,310
Pass | Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	36,822
2019	28,368
2018	33,653
2017	34,303
2016	24,056
Prior	70,059
Revolving Loans Amortized Cost Basis	77,605
Total	304,866		325,991
Pass | Leases
Financing Receivable, Credit Quality Indicator [Line Items]
2020	14,950
2019	19,334
2018	10,342
2017	6,297
2016	2,194
Prior	4,358
Revolving Loans Amortized Cost Basis	0
Total	57,475
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total			99,228
Special Mention | Commercial and Industrial Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	187
2019	546
2018	1,350
2017	2,073
2016	185
Prior	2,137
Revolving Loans Amortized Cost Basis	2,436
Total	8,914
Special Mention | Commercial Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	527
2019	3,038
2018	1,798
2017	4,511
2016	2,025
Prior	15,173
Revolving Loans Amortized Cost Basis	247
Total	27,319		30,504
Special Mention | Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5,444
2019	7,803
2018	2,974
2017	8,713
2016	2,138
Prior	15,763
Revolving Loans Amortized Cost Basis	15,439
Total	58,274		49,053
Special Mention | Leases
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total			46,903
Substandard | Commercial and Industrial Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,167
2019	0
2018	1,193
2017	1,405
2016	976
Prior	5,836
Revolving Loans Amortized Cost Basis	7,778
Total	18,355
Substandard | Commercial Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	1,119
2018	1,995
2017	1,777
2016	4,343
Prior	10,169
Revolving Loans Amortized Cost Basis	0
Total	19,403		16,050
Substandard | Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	611
2019	73
2018	394
2017	1,255
2016	4,467
Prior	6,025
Revolving Loans Amortized Cost Basis	250
Total	13,075		15,827
Substandard | Leases
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Total			0
Doubtful | Commercial and Industrial Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0
Doubtful | Commercial Real Estate Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0		0
Doubtful | Agricultural Loans
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	0		$ 0
Doubtful | Leases
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total	$ 0