Loans and Allowance for Losses - Schedule of Financing Receivables Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	$ 7,393,728	$ 7,233,971
Past due financing receivables	59,691	26,881
Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	6,781,233	6,748,644
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	321,985	252,673
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	290,510	232,654
Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,795,614	3,771,627
Past due financing receivables	25,605	14,821
Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,468,569	3,510,640
Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	173,517	133,526
Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	153,528	127,461
Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,614,897	1,509,821
Past due financing receivables	16,501	3,194
Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,491,299	1,407,272
Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	68,306	51,704
Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	55,292	50,845
Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,391,679	1,355,372
Past due financing receivables	15,963	4,059
Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,253,270	1,256,961
Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	68,338	57,202
Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	70,071	41,209
Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	508,260	504,138
Past due financing receivables	1,622	4,807
Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	485,512	484,075
Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	11,761	8,748
Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	10,987	11,315
Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	78,941	85,181
Past due financing receivables	0	0
Agriculture Storage and Processing [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	78,941	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	4,337	7,832
Past due financing receivables	0	0
Other Commodity [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,642	7,133
Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	63	0
Other Commodity [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	632	699
On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,836,966	4,588,322
Past due financing receivables	55,987	19,577
On-balance sheet [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,464,036	4,335,325
On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	164,157	121,739
On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	208,773	131,258
On-balance sheet [Member] | Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,602,526	2,519,235
Past due financing receivables	24,112	8,345
On-balance sheet [Member] | Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,401,258	2,381,853
On-balance sheet [Member] | Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	92,771	71,096
On-balance sheet [Member] | Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	108,497	66,286
On-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,092,851	989,052
Past due financing receivables	15,598	2,997
On-balance sheet [Member] | Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,006,255	937,793
On-balance sheet [Member] | Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	37,371	14,926
On-balance sheet [Member] | Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	49,225	36,333
On-balance sheet [Member] | Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	782,282	727,113
Past due financing receivables	15,139	4,059
On-balance sheet [Member] | Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	715,900	679,253
On-balance sheet [Member] | Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	23,036	26,499
On-balance sheet [Member] | Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	43,346	21,361
On-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	346,503	336,348
Past due financing receivables	1,138	4,176
On-balance sheet [Member] | Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	327,882	321,345
On-balance sheet [Member] | Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	10,916	7,725
On-balance sheet [Member] | Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,705	7,278
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	11,379	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	11,379	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	1,425	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	1,362	4,477
On-balance sheet [Member] | Other Commodity [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	63	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	2,556,762	2,645,649
Past due financing receivables	3,704	7,304
Off-balance sheet [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,317,197	2,413,319
Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	157,828	130,934
Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	81,737	101,396
Off-balance sheet [Member] | Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,193,088	1,252,392
Past due financing receivables	1,493	6,476
Off-balance sheet [Member] | Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,067,311	1,128,787
Off-balance sheet [Member] | Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	80,746	62,430
Off-balance sheet [Member] | Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	45,031	61,175
Off-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	522,046	520,769
Past due financing receivables	903	197
Off-balance sheet [Member] | Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	485,044	469,479
Off-balance sheet [Member] | Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	30,935	36,778
Off-balance sheet [Member] | Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	6,067	14,512
Off-balance sheet [Member] | Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	609,397	628,259
Past due financing receivables	824	0
Off-balance sheet [Member] | Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	537,370	577,708
Off-balance sheet [Member] | Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	45,302	30,703
Off-balance sheet [Member] | Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	26,725	19,848
Off-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	161,757	167,790
Past due financing receivables	484	631
Off-balance sheet [Member] | Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	157,630	162,730
Off-balance sheet [Member] | Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	845	1,023
Off-balance sheet [Member] | Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,282	4,037
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	67,562	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	67,562	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	2,912	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	2,280	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	$ 632	$ 699