Loans - Schedule of Financing Receivables Credit Quality Indicators (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
2020
Current period recoveries	$ 0
2019
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
2017
Financing Receivable, Originated Three Years before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
2016
Financing Receivable, Originated Four Years before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
Prior
Financing Receivable, Originated Five or More Years before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
Revolving Loans - Amortized Cost Basis
Financing Receivable, Revolving, Allowance for Credit Loss, Recovery	0
Total
Total	7,261,933	$ 5,390,977
Current period charge-offs	5,800
90-Days Delinquencies	6,286
On-Balance Sheet:
Total
Total		5,276,557
On-Balance Sheet: | Crops
Total
Total		2,773,177
On-Balance Sheet: | Permanent Plantings
Total
Total		1,213,156
On-Balance Sheet: | Livestock
Total
Total		911,303
On-Balance Sheet: | Part-time Farm
Total
Total		363,964
On-Balance Sheet: | Ag. Storage and Processing
Total
Total		10,360
On-Balance Sheet: | Other
Total
Total		4,597
Farm & Ranch
2020
Total	2,021,189
Current period charge-offs	0
Current period recoveries	0
Current period Farm & Ranch net charge-offs	0
2019
Total	859,880
Current period charge-offs	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	0
2018
Total	524,541
Current period charge-offs	0
Financing Receivable, Originated Two Years before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	0
2017
Total	562,007
Current period charge-offs	5,365
Financing Receivable, Originated Three Years before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	5,365
2016
Total	515,561
Current period charge-offs	0
Financing Receivable, Originated Four Years before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	0
Prior
Total	1,140,603
Current period charge-offs	394
Financing Receivable, Originated Five or More Years before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	394
Revolving Loans - Amortized Cost Basis
Total	552,657
Current period charge-offs	0
Financing Receivable, Revolving, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	0
Total
Total	6,176,438
Current period charge-offs	5,759
Financing Receivable, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	5,759	67	$ 17
90-Days Delinquencies	6,286
Farm & Ranch | On-Balance Sheet:
Total
Total		5,276,557
90-Days Delinquencies		57,719
Farm & Ranch | On-Balance Sheet: | Crops
Total
Total		2,773,177
90-Days Delinquencies		21,167
Farm & Ranch | On-Balance Sheet: | Permanent Plantings
Total
Total		1,213,156
90-Days Delinquencies		15,828
Farm & Ranch | On-Balance Sheet: | Livestock
Total
Total		911,303
90-Days Delinquencies		19,354
Farm & Ranch | On-Balance Sheet: | Part-time Farm
Total
Total		363,964
90-Days Delinquencies		1,370
Farm & Ranch | On-Balance Sheet: | Ag. Storage and Processing
Total
Total		10,360
90-Days Delinquencies		0
Farm & Ranch | On-Balance Sheet: | Other
Total
Total		4,597
90-Days Delinquencies		0
Rural Utilities:
2020
Total	667,489
Current period charge-offs	0
Current period Farm & Ranch net charge-offs	0
2019
Total	809,921
Current period charge-offs	0
Current period Farm & Ranch net charge-offs	0
2018
Total	8,260
Current period charge-offs	0
Financing Receivable, Originated Two Years before Latest Fiscal Year, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	0
2017
Total	89,842
Current period charge-offs	0
Current period Farm & Ranch net charge-offs	0
2016
Total	31,275
Current period charge-offs	0
Current period Farm & Ranch net charge-offs	0
Prior
Total	641,145
Current period charge-offs	0
Current period Farm & Ranch net charge-offs	0
Revolving Loans - Amortized Cost Basis
Total	12,480
Current period charge-offs	0
Current period Farm & Ranch net charge-offs	0
Total
Total	2,260,412
Current period charge-offs	0
Financing Receivable, Allowance for Credit Loss, Recovery	0
Current period Farm & Ranch net charge-offs	0	0	$ 0
90-Days Delinquencies	0
Acceptable | Farm & Ranch
2020
Total	1,947,618
2019
Total	774,315
2018
Total	484,345
2017
Total	500,768
2016
Total	465,277
Prior
Total	1,068,693
Revolving Loans - Amortized Cost Basis
Total	535,742
Total
Total	5,776,758
Acceptable | Farm & Ranch | On-Balance Sheet:
Total
Total		4,790,636
Acceptable | Farm & Ranch | On-Balance Sheet: | Crops
Total
Total		2,556,956
Acceptable | Farm & Ranch | On-Balance Sheet: | Permanent Plantings
Total
Total		1,050,160
Acceptable | Farm & Ranch | On-Balance Sheet: | Livestock
Total
Total		825,234
Acceptable | Farm & Ranch | On-Balance Sheet: | Part-time Farm
Total
Total		343,329
Acceptable | Farm & Ranch | On-Balance Sheet: | Ag. Storage and Processing
Total
Total		10,360
Acceptable | Farm & Ranch | On-Balance Sheet: | Other
Total
Total		4,597
Acceptable | Rural Utilities:
2020
Total	667,489
2019
Total	809,921
2018
Total	8,260
2017
Total	89,842
2016
Total	31,275
Prior
Total	641,145
Revolving Loans - Amortized Cost Basis
Total	12,480
Total
Total	2,260,412
Special mention | Farm & Ranch
2020
Total	70,171
2019
Total	79,744
2018
Total	18,317
2017
Total	8,530
2016
Total	13,111
Prior
Total	21,328
Revolving Loans - Amortized Cost Basis
Total	7,656
Total
Total	218,857
Special mention | Farm & Ranch | On-Balance Sheet:
Total
Total		278,843
Special mention | Farm & Ranch | On-Balance Sheet: | Crops
Total
Total		107,406
Special mention | Farm & Ranch | On-Balance Sheet: | Permanent Plantings
Total
Total		111,739
Special mention | Farm & Ranch | On-Balance Sheet: | Livestock
Total
Total		46,107
Special mention | Farm & Ranch | On-Balance Sheet: | Part-time Farm
Total
Total		13,591
Special mention | Farm & Ranch | On-Balance Sheet: | Ag. Storage and Processing
Total
Total		0
Special mention | Farm & Ranch | On-Balance Sheet: | Other
Total
Total		0
Special mention | Rural Utilities:
2020
Total	0
2019
Total	0
2018
Total	0
2017
Total	0
2016
Total	0
Prior
Total	0
Revolving Loans - Amortized Cost Basis
Total	0
Total
Total	0
Substandard | Farm & Ranch
2020
Total	3,400
2019
Total	5,821
2018
Total	21,879
2017
Total	52,709
2016
Total	37,173
Prior
Total	50,582
Revolving Loans - Amortized Cost Basis
Total	9,259
Total
Total	180,823
Substandard | Farm & Ranch | On-Balance Sheet:
Total
Total		207,078
Substandard | Farm & Ranch | On-Balance Sheet: | Crops
Total
Total		108,815
Substandard | Farm & Ranch | On-Balance Sheet: | Permanent Plantings
Total
Total		51,257
Substandard | Farm & Ranch | On-Balance Sheet: | Livestock
Total
Total		39,962
Substandard | Farm & Ranch | On-Balance Sheet: | Part-time Farm
Total
Total		7,044
Substandard | Farm & Ranch | On-Balance Sheet: | Ag. Storage and Processing
Total
Total		0
Substandard | Farm & Ranch | On-Balance Sheet: | Other
Total
Total		$ 0
Substandard | Rural Utilities:
2020
Total	0
2019
Total	0
2018
Total	0
2017
Total	0
2016
Total	0
Prior
Total	0
Revolving Loans - Amortized Cost Basis
Total	0
Total
Total	$ 0