Loans and Allowance for Losses - Schedule of Financing Receivables Credit Quality Indicators (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	$ 7,776,950	$ 7,233,971
Past due financing receivables	60,954	26,881
Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,059,641	6,748,644
Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	407,354	252,673
Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	309,955	232,654
Crops
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,930,858	3,771,627
Past due financing receivables	22,660	14,821
Crops | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,589,958	3,510,640
Crops | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	175,778	133,526
Crops | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	165,122	127,461
Permanent Plantings
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,727,261	1,509,821
Past due financing receivables	16,024	3,194
Permanent Plantings | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,534,761	1,407,272
Permanent Plantings | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	134,648	51,704
Permanent Plantings | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	57,852	50,845
Livestock
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,502,887	1,355,372
Past due financing receivables	20,420	4,059
Livestock | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,346,575	1,256,961
Livestock | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	81,725	57,202
Livestock | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	74,587	41,209
Part-time Farm
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	532,065	504,138
Past due financing receivables	1,850	4,807
Part-time Farm | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	504,690	484,075
Part-time Farm | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	15,203	8,748
Part-time Farm | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	12,172	11,315
Ag. Storage and Processing
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	76,466	85,181
Past due financing receivables	0	0
Ag. Storage and Processing | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	76,466	82,563
Ag. Storage and Processing | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	1,493
Ag. Storage and Processing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	1,125
Other
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,413	7,832
Past due financing receivables	0	0
Other | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,191	7,133
Other | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	222	699
On-Balance Sheet:
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	5,276,557	4,588,322
Past due financing receivables	57,719	19,577
On-Balance Sheet: | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,790,636	4,335,325
On-Balance Sheet: | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	278,843	121,739
On-Balance Sheet: | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	207,078	131,258
On-Balance Sheet: | Crops
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,773,177	2,519,235
Past due financing receivables	21,167	8,345
On-Balance Sheet: | Crops | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,556,956	2,381,853
On-Balance Sheet: | Crops | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	107,406	71,096
On-Balance Sheet: | Crops | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	108,815	66,286
On-Balance Sheet: | Permanent Plantings
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,213,156	989,052
Past due financing receivables	15,828	2,997
On-Balance Sheet: | Permanent Plantings | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,050,160	937,793
On-Balance Sheet: | Permanent Plantings | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	111,739	14,926
On-Balance Sheet: | Permanent Plantings | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	51,257	36,333
On-Balance Sheet: | Livestock
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	911,303	727,113
Past due financing receivables	19,354	4,059
On-Balance Sheet: | Livestock | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	825,234	679,253
On-Balance Sheet: | Livestock | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	46,107	26,499
On-Balance Sheet: | Livestock | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	39,962	21,361
On-Balance Sheet: | Part-time Farm
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	363,964	336,348
Past due financing receivables	1,370	4,176
On-Balance Sheet: | Part-time Farm | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	343,329	321,345
On-Balance Sheet: | Part-time Farm | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	13,591	7,725
On-Balance Sheet: | Part-time Farm | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,044	7,278
On-Balance Sheet: | Ag. Storage and Processing
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	10,360	12,097
Past due financing receivables	0	0
On-Balance Sheet: | Ag. Storage and Processing | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	10,360	10,604
On-Balance Sheet: | Ag. Storage and Processing | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	1,493
On-Balance Sheet: | Ag. Storage and Processing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
On-Balance Sheet: | Other
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,597	4,477
Past due financing receivables	0	0
On-Balance Sheet: | Other | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,597	4,477
On-Balance Sheet: | Other | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
On-Balance Sheet: | Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
Off-Balance Sheet:
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,500,393	2,645,649
Past due financing receivables	3,235	7,304
Off-Balance Sheet: | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,269,005	2,413,319
Off-Balance Sheet: | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	128,511	130,934
Off-Balance Sheet: | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	102,877	101,396
Off-Balance Sheet: | Crops
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,157,681	1,252,392
Past due financing receivables	1,493	6,476
Off-Balance Sheet: | Crops | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,033,002	1,128,787
Off-Balance Sheet: | Crops | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	68,372	62,430
Off-Balance Sheet: | Crops | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	56,307	61,175
Off-Balance Sheet: | Permanent Plantings
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	514,105	520,769
Past due financing receivables	196	197
Off-Balance Sheet: | Permanent Plantings | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	484,601	469,479
Off-Balance Sheet: | Permanent Plantings | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	22,909	36,778
Off-Balance Sheet: | Permanent Plantings | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	6,595	14,512
Off-Balance Sheet: | Livestock
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	591,584	628,259
Past due financing receivables	1,066	0
Off-Balance Sheet: | Livestock | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	521,341	577,708
Off-Balance Sheet: | Livestock | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	35,618	30,703
Off-Balance Sheet: | Livestock | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	34,625	19,848
Off-Balance Sheet: | Part-time Farm
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	168,101	167,790
Past due financing receivables	480	631
Off-Balance Sheet: | Part-time Farm | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	161,361	162,730
Off-Balance Sheet: | Part-time Farm | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,612	1,023
Off-Balance Sheet: | Part-time Farm | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	5,128	4,037
Off-Balance Sheet: | Ag. Storage and Processing
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	66,106	73,084
Past due financing receivables	0	0
Off-Balance Sheet: | Ag. Storage and Processing | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	66,106	71,959
Off-Balance Sheet: | Ag. Storage and Processing | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
Off-Balance Sheet: | Ag. Storage and Processing | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	1,125
Off-Balance Sheet: | Other
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,816	3,355
Past due financing receivables	0	0
Off-Balance Sheet: | Other | Acceptable
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,594	2,656
Off-Balance Sheet: | Other | Special mention
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
Off-Balance Sheet: | Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	$ 222	$ 699