Loans - Schedule of Financing Receivables Credit Quality Indicators (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
2020
Current period recoveries	$ 0		$ 0
2019
Current period recoveries	0		0
2017
Current period recoveries	0		0
2016
Current period recoveries	0		0
Prior
Current period recoveries	0		0
Revolving Loans - Amortized Cost Basis
Current period recoveries	0		0
Total
Total	6,825,061		6,825,061		$ 5,390,977
Current period charge-offs			100
90-Days Delinquencies	11,051		11,051		57,700
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	1,470,275		1,470,275
Current period charge-offs	0		0
Current period recoveries	0		0
Current period net charge-offs	0		0
2019
Total	895,361		895,361
Current period charge-offs	0		0
Current period recoveries	0		0
Current period net charge-offs	0		0
2018
Total	554,657		554,657
Current period charge-offs	0		0
Current period recoveries	0		0
Current period net charge-offs	0		0
2017
Total	619,269		619,269
Current period charge-offs	0		0
Current period recoveries	0		0
Current period net charge-offs	0		0
2016
Total	547,029		547,029
Current period charge-offs	0		0
Current period recoveries	0		0
Current period net charge-offs	0		0
Prior
Total	1,239,199		1,239,199
Current period charge-offs	0		394
Current period recoveries	0		0
Current period net charge-offs	0		394
Revolving Loans - Amortized Cost Basis
Total	531,534		531,534
Current period charge-offs	0		0
Current period recoveries	0		0
Current period net charge-offs	0		0
Total
Total	5,857,324		5,857,324
Current period charge-offs	0		394
Current period recoveries	0		0
Current period net charge-offs	0	$ 0	394	$ 67
90-Days Delinquencies	11,051		11,051
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	502,873		502,873
Current period charge-offs	0		0
Current period net charge-offs	0		0
2019
Total	819,099		819,099
Current period charge-offs	0		0
Current period net charge-offs	0		0
2018
Total	8,260		8,260
Current period charge-offs	0		0
Current period recoveries	0		0
Current period net charge-offs	0		0
2017
Total	92,223		92,223
Current period charge-offs	0		0
Current period net charge-offs	0		0
2016
Total	31,275		31,275
Current period charge-offs	0		0
Current period net charge-offs	0		0
Prior
Total	642,755		642,755
Current period charge-offs	0		0
Current period net charge-offs	0		0
Revolving Loans - Amortized Cost Basis
Total	12,870		12,870
Current period charge-offs	0		0
Current period net charge-offs	0		0
Total
Total	2,109,355		2,109,355
Current period charge-offs	0		0
Current period recoveries	0		0
Current period net charge-offs	0	$ 0	0	$ 0
90-Days Delinquencies	0		0
Acceptable | Farm & Ranch
2020
Total	1,423,112		1,423,112
2019
Total	765,367		765,367
2018
Total	507,218		507,218
2017
Total	557,095		557,095
2016
Total	499,642		499,642
Prior
Total	1,157,633		1,157,633
Revolving Loans - Amortized Cost Basis
Total	472,209		472,209
Total
Total	5,382,276		5,382,276
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	502,873		502,873
2019
Total	819,099		819,099
2018
Total	8,260		8,260
2017
Total	92,223		92,223
2016
Total	31,275		31,275
Prior
Total	638,281		638,281
Revolving Loans - Amortized Cost Basis
Total	12,870		12,870
Total
Total	2,104,881		2,104,881
Special mention | Farm & Ranch
2020
Total	39,607		39,607
2019
Total	124,068		124,068
2018
Total	27,757		27,757
2017
Total	4,633		4,633
2016
Total	10,897		10,897
Prior
Total	22,236		22,236
Revolving Loans - Amortized Cost Basis
Total	50,395		50,395
Total
Total	279,593		279,593
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		0
2019
Total	0		0
2018
Total	0		0
2017
Total	0		0
2016
Total	0		0
Prior
Total	0		0
Revolving Loans - Amortized Cost Basis
Total	0		0
Total
Total	0		0
Substandard | Farm & Ranch
2020
Total	7,556		7,556
2019
Total	5,926		5,926
2018
Total	19,682		19,682
2017
Total	57,541		57,541
2016
Total	36,490		36,490
Prior
Total	59,330		59,330
Revolving Loans - Amortized Cost Basis
Total	8,930		8,930
Total
Total	195,455		195,455
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		0
2019
Total	0		0
2018
Total	0		0
2017
Total	0		0
2016
Total	0		0
Prior
Total	4,474		4,474
Revolving Loans - Amortized Cost Basis
Total	0		0
Total
Total	$ 4,474		$ 4,474