Loans and Allowance for Losses - Schedule of Financing Receivables Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	$ 7,215,585	$ 7,233,971
Past due financing receivables	52,366	26,881
Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	6,685,093	6,748,644
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	283,776	252,673
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	246,716	232,654
Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,763,456	3,771,627
Past due financing receivables	34,509	14,821
Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,479,661	3,510,640
Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	140,396	133,526
Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	143,399	127,461
Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,492,359	1,509,821
Past due financing receivables	8,125	3,194
Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,378,328	1,407,272
Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	69,711	51,704
Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	44,320	50,845
Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,350,610	1,355,372
Past due financing receivables	6,845	4,059
Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,241,412	1,256,961
Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	62,035	57,202
Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	47,163	41,209
Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	517,110	504,138
Past due financing receivables	2,887	4,807
Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	496,930	484,075
Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	10,137	8,748
Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	10,043	11,315
Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	84,321	85,181
Past due financing receivables	0	0
Agriculture Storage and Processing [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	81,699	82,563
Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,497	1,493
Agriculture Storage and Processing [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,125	1,125
Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,729	7,832
Past due financing receivables	0	0
Other Commodity [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,063	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	666	699
On-balance sheet [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,610,897	4,588,322
Past due financing receivables	47,219	19,577
On-balance sheet [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	4,322,621	4,335,325
On-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	131,895	121,739
On-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	156,381	131,258
On-balance sheet [Member] | Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,537,102	2,519,235
Past due financing receivables	30,149	8,345
On-balance sheet [Member] | Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,391,354	2,381,853
On-balance sheet [Member] | Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	59,594	71,096
On-balance sheet [Member] | Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	86,154	66,286
On-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	983,220	989,052
Past due financing receivables	7,929	2,997
On-balance sheet [Member] | Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	901,684	937,793
On-balance sheet [Member] | Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	44,751	14,926
On-balance sheet [Member] | Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	36,785	36,333
On-balance sheet [Member] | Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	726,397	727,113
Past due financing receivables	6,745	4,059
On-balance sheet [Member] | Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	682,548	679,253
On-balance sheet [Member] | Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	16,786	26,499
On-balance sheet [Member] | Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	27,063	21,361
On-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	347,556	336,348
Past due financing receivables	2,396	4,176
On-balance sheet [Member] | Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	331,910	321,345
On-balance sheet [Member] | Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	9,267	7,725
On-balance sheet [Member] | Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	6,379	7,278
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	12,036	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	10,539	10,604
On-balance sheet [Member] | Agriculture Storage and Processing [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,497	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	4,586	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	4,586	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	2,604,688	2,645,649
Past due financing receivables	5,147	7,304
Off-balance sheet [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	2,362,472	2,413,319
Off-balance sheet [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	151,881	130,934
Off-balance sheet [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	90,335	101,396
Off-balance sheet [Member] | Crops [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,226,354	1,252,392
Past due financing receivables	4,360	6,476
Off-balance sheet [Member] | Crops [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	1,088,307	1,128,787
Off-balance sheet [Member] | Crops [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	80,802	62,430
Off-balance sheet [Member] | Crops [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	57,245	61,175
Off-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	509,139	520,769
Past due financing receivables	196	197
Off-balance sheet [Member] | Permanent Plantings [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	476,644	469,479
Off-balance sheet [Member] | Permanent Plantings [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	24,960	36,778
Off-balance sheet [Member] | Permanent Plantings [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	7,535	14,512
Off-balance sheet [Member] | Livestock [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	624,213	628,259
Past due financing receivables	100	0
Off-balance sheet [Member] | Livestock [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	558,864	577,708
Off-balance sheet [Member] | Livestock [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	45,249	30,703
Off-balance sheet [Member] | Livestock [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	20,100	19,848
Off-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	169,554	167,790
Past due financing receivables	491	631
Off-balance sheet [Member] | Part-Time Farm [Member] | Acceptable [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	165,020	162,730
Off-balance sheet [Member] | Part-Time Farm [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	870	1,023
Off-balance sheet [Member] | Part-Time Farm [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,664	4,037
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	72,285	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	71,160	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	1,125	1,125
Off-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Recorded Investment [Line Items]
Gross financing receivables	3,143	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	2,477	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	$ 666	$ 699