Loans and Allowance for Losses - Schedule of Financing Receivables Credit Quality Indicators (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	$ 7,291,352	$ 7,233,971
Past due financing receivables	28,045	26,881
Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	6,737,569	6,748,644
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	311,080	252,673
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	242,703	232,654
Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,785,746	3,771,627
Past due financing receivables	15,383	14,821
Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,491,461	3,510,640
Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	157,169	133,526
Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	137,116	127,461
Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,552,572	1,509,821
Past due financing receivables	4,286	3,194
Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,434,810	1,407,272
Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	73,071	51,704
Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	44,691	50,845
Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,360,281	1,355,372
Past due financing receivables	5,982	4,059
Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,243,567	1,256,961
Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	67,302	57,202
Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	49,412	41,209
Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	504,553	504,138
Past due financing receivables	2,394	4,807
Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	480,187	484,075
Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	13,538	8,748
Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	10,828	11,315
Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	80,560	85,181
Past due financing receivables	0	0
Agriculture Storage and Processing [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	80,560	82,563
Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	1,493
Agriculture Storage and Processing [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	1,125
Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,640	7,832
Past due financing receivables	0	0
Other Commodity [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	6,984	7,133
Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
Other Commodity [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	656	699
On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,754,258	4,588,322
Past due financing receivables	20,812	19,577
On-balance sheet [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,421,918	4,335,325
On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	175,843	121,739
On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	156,497	131,258
On-balance sheet [Member] | Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,592,330	2,519,235
Past due financing receivables	10,677	8,345
On-balance sheet [Member] | Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,421,677	2,381,853
On-balance sheet [Member] | Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	79,905	71,096
On-balance sheet [Member] | Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	90,748	66,286
On-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,057,872	989,052
Past due financing receivables	3,375	2,997
On-balance sheet [Member] | Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	972,075	937,793
On-balance sheet [Member] | Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	49,178	14,926
On-balance sheet [Member] | Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	36,619	36,333
On-balance sheet [Member] | Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	747,527	727,113
Past due financing receivables	4,854	4,059
On-balance sheet [Member] | Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	691,516	679,253
On-balance sheet [Member] | Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	34,079	26,499
On-balance sheet [Member] | Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	21,932	21,361
On-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	340,328	336,348
Past due financing receivables	1,906	4,176
On-balance sheet [Member] | Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	320,449	321,345
On-balance sheet [Member] | Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	12,681	7,725
On-balance sheet [Member] | Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,198	7,278
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	11,581	12,097
Past due financing receivables	0	0
On-balance sheet [Member] | Agriculture Storage and Processing [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	11,581	10,604
On-balance sheet [Member] | Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	1,493
On-balance sheet [Member] | Agriculture Storage and Processing [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
On-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,620	4,477
Past due financing receivables	0	0
On-balance sheet [Member] | Other Commodity [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,620	4,477
On-balance sheet [Member] | Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
On-balance sheet [Member] | Other Commodity [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
Off-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,537,094	2,645,649
Past due financing receivables	7,233	7,304
Off-balance sheet [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,315,651	2,413,319
Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	135,237	130,934
Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	86,206	101,396
Off-balance sheet [Member] | Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,193,416	1,252,392
Past due financing receivables	4,706	6,476
Off-balance sheet [Member] | Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,069,784	1,128,787
Off-balance sheet [Member] | Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	77,264	62,430
Off-balance sheet [Member] | Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	46,368	61,175
Off-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	494,700	520,769
Past due financing receivables	911	197
Off-balance sheet [Member] | Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	462,735	469,479
Off-balance sheet [Member] | Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	23,893	36,778
Off-balance sheet [Member] | Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	8,072	14,512
Off-balance sheet [Member] | Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	612,754	628,259
Past due financing receivables	1,128	0
Off-balance sheet [Member] | Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	552,051	577,708
Off-balance sheet [Member] | Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	33,223	30,703
Off-balance sheet [Member] | Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	27,480	19,848
Off-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	164,225	167,790
Past due financing receivables	488	631
Off-balance sheet [Member] | Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	159,738	162,730
Off-balance sheet [Member] | Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	857	1,023
Off-balance sheet [Member] | Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,630	4,037
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	68,979	73,084
Past due financing receivables	0	0
Off-balance sheet [Member] | Agriculture Storage and Processing [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	68,979	71,959
Off-balance sheet [Member] | Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
Off-balance sheet [Member] | Agriculture Storage and Processing [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	1,125
Off-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,020	3,355
Past due financing receivables	0	0
Off-balance sheet [Member] | Other Commodity [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,364	2,656
Off-balance sheet [Member] | Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	0	0
Off-balance sheet [Member] | Other Commodity [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	$ 656	$ 699