Loans and Allowance for Losses - Schedule of Allowance for Losses by Impairment Method and Commodity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	$ 7,172,973		$ 7,079,331
Individually evaluated for impairment:	220,755		154,640
Total Farm & Ranch loans:	7,393,728		7,233,971
Allowance for Losses:
Collectively evaluated for impairment:	4,975		5,779
Individually evaluated for impairment:	4,792		3,405
Total Farm & Ranch loans:	9,767	$ 9,144	9,184	$ 9,018	$ 9,038	$ 8,866
Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	3,682,001		3,691,897
Individually evaluated for impairment:	113,613		79,730
Total Farm & Ranch loans:	3,795,614		3,771,627
Allowance for Losses:
Collectively evaluated for impairment:	2,285		2,788
Individually evaluated for impairment:	2,576		1,606
Total Farm & Ranch loans:	4,861	4,773	4,394	4,026	4,125	4,081
Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,563,550		1,468,239
Individually evaluated for impairment:	51,347		41,582
Total Farm & Ranch loans:	1,614,897		1,509,821
Allowance for Losses:
Collectively evaluated for impairment:	991		992
Individually evaluated for impairment:	1,114		1,134
Total Farm & Ranch loans:	2,105	1,926	2,126	2,408	2,368	2,469
Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,344,358		1,330,274
Individually evaluated for impairment:	47,321		25,098
Total Farm & Ranch loans:	1,391,679		1,355,372
Allowance for Losses:
Collectively evaluated for impairment:	844		938
Individually evaluated for impairment:	983		522
Total Farm & Ranch loans:	1,827	1,423	1,460	1,470	1,322	1,211
Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	499,843		495,977
Individually evaluated for impairment:	8,417		8,161
Total Farm & Ranch loans:	508,260		504,138
Allowance for Losses:
Collectively evaluated for impairment:	265		332
Individually evaluated for impairment:	119		142
Total Farm & Ranch loans:	384	400	474	481	448	481
Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	78,941		85,181
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	78,941		85,181
Allowance for Losses:
Collectively evaluated for impairment:	585		720
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	585	603	720	623	720	606
Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	4,280		7,763
Individually evaluated for impairment:	57		69
Total Farm & Ranch loans:	4,337		7,832
Allowance for Losses:
Collectively evaluated for impairment:	5		9
Individually evaluated for impairment:	0		1
Total Farm & Ranch loans:	5	$ 19	10	$ 10	$ 55	$ 18
On-balance sheet [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	4,628,193		4,456,918
Individually evaluated for impairment:	208,773		131,404
Total Farm & Ranch loans:	4,836,966		4,588,322
Allowance for Losses:
Collectively evaluated for impairment:	3,435		4,064
Individually evaluated for impairment:	4,589		2,953
Total Farm & Ranch loans:	8,024		7,017
On-balance sheet [Member] | Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	2,494,029		2,452,803
Individually evaluated for impairment:	108,497		66,432
Total Farm & Ranch loans:	2,602,526		2,519,235
Allowance for Losses:
Collectively evaluated for impairment:	1,729		2,120
Individually evaluated for impairment:	2,495		1,329
Total Farm & Ranch loans:	4,224		3,449
On-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,043,626		952,719
Individually evaluated for impairment:	49,225		36,333
Total Farm & Ranch loans:	1,092,851		989,052
Allowance for Losses:
Collectively evaluated for impairment:	885		822
Individually evaluated for impairment:	1,070		1,065
Total Farm & Ranch loans:	1,955		1,887
On-balance sheet [Member] | Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	738,936		705,752
Individually evaluated for impairment:	43,346		21,361
Total Farm & Ranch loans:	782,282		727,113
Allowance for Losses:
Collectively evaluated for impairment:	550		731
Individually evaluated for impairment:	920		437
Total Farm & Ranch loans:	1,470		1,168
On-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	338,798		329,070
Individually evaluated for impairment:	7,705		7,278
Total Farm & Ranch loans:	346,503		336,348
Allowance for Losses:
Collectively evaluated for impairment:	242		303
Individually evaluated for impairment:	104		122
Total Farm & Ranch loans:	346		425
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	11,379		12,097
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	11,379		12,097
Allowance for Losses:
Collectively evaluated for impairment:	28		84
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	28		84
On-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,425		4,477
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	1,425		4,477
Allowance for Losses:
Collectively evaluated for impairment:	1		4
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	1		4
Off-balance sheet [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	2,544,780		2,622,413
Individually evaluated for impairment:	11,982		23,236
Total Farm & Ranch loans:	2,556,762		2,645,649
Allowance for Losses:
Collectively evaluated for impairment:	1,540		1,715
Individually evaluated for impairment:	203		452
Total Farm & Ranch loans:	1,743		2,167
Off-balance sheet [Member] | Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,187,972		1,239,094
Individually evaluated for impairment:	5,116		13,298
Total Farm & Ranch loans:	1,193,088		1,252,392
Allowance for Losses:
Collectively evaluated for impairment:	556		668
Individually evaluated for impairment:	81		277
Total Farm & Ranch loans:	637		945
Off-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	519,924		515,520
Individually evaluated for impairment:	2,122		5,249
Total Farm & Ranch loans:	522,046		520,769
Allowance for Losses:
Collectively evaluated for impairment:	106		170
Individually evaluated for impairment:	44		69
Total Farm & Ranch loans:	150		239
Off-balance sheet [Member] | Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	605,422		624,522
Individually evaluated for impairment:	3,975		3,737
Total Farm & Ranch loans:	609,397		628,259
Allowance for Losses:
Collectively evaluated for impairment:	294		207
Individually evaluated for impairment:	63		85
Total Farm & Ranch loans:	357		292
Off-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	161,045		166,907
Individually evaluated for impairment:	712		883
Total Farm & Ranch loans:	161,757		167,790
Allowance for Losses:
Collectively evaluated for impairment:	23		29
Individually evaluated for impairment:	15		20
Total Farm & Ranch loans:	38		49
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	67,562		73,084
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	67,562		73,084
Allowance for Losses:
Collectively evaluated for impairment:	557		636
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	557		636
Off-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	2,855		3,286
Individually evaluated for impairment:	57		69
Total Farm & Ranch loans:	2,912		3,355
Allowance for Losses:
Collectively evaluated for impairment:	4		5
Individually evaluated for impairment:	0		1
Total Farm & Ranch loans:	$ 4		$ 6