Loans and Allowance for Losses - Schedule of Allowance for Losses by Impairment Method and Commodity (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	$ 7,119,554		$ 7,079,331
Individually evaluated for impairment:	171,798		154,640
Total Farm & Ranch loans:	7,291,352		7,233,971
Allowance for Losses:
Collectively evaluated for impairment:	5,299		5,779
Individually evaluated for impairment:	3,845		3,405
Total Farm & Ranch loans:	9,144	$ 8,791	9,184	$ 9,038	$ 8,456	$ 8,866
Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	3,686,986		3,691,897
Individually evaluated for impairment:	98,760		79,730
Total Farm & Ranch loans:	3,785,746		3,771,627
Allowance for Losses:
Collectively evaluated for impairment:	2,429		2,788
Individually evaluated for impairment:	2,344		1,606
Total Farm & Ranch loans:	4,773	4,233	4,394	4,125	3,793	4,081
Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,513,825		1,468,239
Individually evaluated for impairment:	38,747		41,582
Total Farm & Ranch loans:	1,552,572		1,509,821
Allowance for Losses:
Collectively evaluated for impairment:	1,044		992
Individually evaluated for impairment:	882		1,134
Total Farm & Ranch loans:	1,926	1,934	2,126	2,368	2,479	2,469
Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,334,106		1,330,274
Individually evaluated for impairment:	26,175		25,098
Total Farm & Ranch loans:	1,360,281		1,355,372
Allowance for Losses:
Collectively evaluated for impairment:	928		938
Individually evaluated for impairment:	495		522
Total Farm & Ranch loans:	1,423	1,452	1,460	1,322	1,236	1,211
Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	496,495		495,977
Individually evaluated for impairment:	8,058		8,161
Total Farm & Ranch loans:	504,553		504,138
Allowance for Losses:
Collectively evaluated for impairment:	276		332
Individually evaluated for impairment:	124		142
Total Farm & Ranch loans:	400	413	474	448	413	481
Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	80,560		85,181
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	80,560		85,181
Allowance for Losses:
Collectively evaluated for impairment:	603		720
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	603	737	720	720	522	606
Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	7,582		7,763
Individually evaluated for impairment:	58		69
Total Farm & Ranch loans:	7,640		7,832
Allowance for Losses:
Collectively evaluated for impairment:	19		9
Individually evaluated for impairment:	0		1
Total Farm & Ranch loans:	19	$ 22	10	$ 55	$ 13	$ 18
On-balance sheet [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	4,597,618		4,456,918
Individually evaluated for impairment:	156,640		131,404
Total Farm & Ranch loans:	4,754,258		4,588,322
Allowance for Losses:
Collectively evaluated for impairment:	3,714		4,064
Individually evaluated for impairment:	3,550		2,953
Total Farm & Ranch loans:	7,264		7,017
On-balance sheet [Member] | Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	2,501,439		2,452,803
Individually evaluated for impairment:	90,891		66,432
Total Farm & Ranch loans:	2,592,330		2,519,235
Allowance for Losses:
Collectively evaluated for impairment:	1,817		2,120
Individually evaluated for impairment:	2,194		1,329
Total Farm & Ranch loans:	4,011		3,449
On-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,021,253		952,719
Individually evaluated for impairment:	36,619		36,333
Total Farm & Ranch loans:	1,057,872		989,052
Allowance for Losses:
Collectively evaluated for impairment:	932		822
Individually evaluated for impairment:	832		1,065
Total Farm & Ranch loans:	1,764		1,887
On-balance sheet [Member] | Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	725,595		705,752
Individually evaluated for impairment:	21,932		21,361
Total Farm & Ranch loans:	747,527		727,113
Allowance for Losses:
Collectively evaluated for impairment:	651		731
Individually evaluated for impairment:	418		437
Total Farm & Ranch loans:	1,069		1,168
On-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	333,130		329,070
Individually evaluated for impairment:	7,198		7,278
Total Farm & Ranch loans:	340,328		336,348
Allowance for Losses:
Collectively evaluated for impairment:	251		303
Individually evaluated for impairment:	106		122
Total Farm & Ranch loans:	357		425
On-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	11,581		12,097
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	11,581		12,097
Allowance for Losses:
Collectively evaluated for impairment:	49		84
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	49		84
On-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	4,620		4,477
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	4,620		4,477
Allowance for Losses:
Collectively evaluated for impairment:	14		4
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	14		4
Off-balance sheet [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	2,521,936		2,622,413
Individually evaluated for impairment:	15,158		23,236
Total Farm & Ranch loans:	2,537,094		2,645,649
Allowance for Losses:
Collectively evaluated for impairment:	1,585		1,715
Individually evaluated for impairment:	295		452
Total Farm & Ranch loans:	1,880		2,167
Off-balance sheet [Member] | Crops [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	1,185,547		1,239,094
Individually evaluated for impairment:	7,869		13,298
Total Farm & Ranch loans:	1,193,416		1,252,392
Allowance for Losses:
Collectively evaluated for impairment:	612		668
Individually evaluated for impairment:	150		277
Total Farm & Ranch loans:	762		945
Off-balance sheet [Member] | Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	492,572		515,520
Individually evaluated for impairment:	2,128		5,249
Total Farm & Ranch loans:	494,700		520,769
Allowance for Losses:
Collectively evaluated for impairment:	112		170
Individually evaluated for impairment:	50		69
Total Farm & Ranch loans:	162		239
Off-balance sheet [Member] | Livestock [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	608,511		624,522
Individually evaluated for impairment:	4,243		3,737
Total Farm & Ranch loans:	612,754		628,259
Allowance for Losses:
Collectively evaluated for impairment:	277		207
Individually evaluated for impairment:	77		85
Total Farm & Ranch loans:	354		292
Off-balance sheet [Member] | Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	163,365		166,907
Individually evaluated for impairment:	860		883
Total Farm & Ranch loans:	164,225		167,790
Allowance for Losses:
Collectively evaluated for impairment:	25		29
Individually evaluated for impairment:	18		20
Total Farm & Ranch loans:	43		49
Off-balance sheet [Member] | Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	68,979		73,084
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	68,979		73,084
Allowance for Losses:
Collectively evaluated for impairment:	554		636
Individually evaluated for impairment:	0		0
Total Farm & Ranch loans:	554		636
Off-balance sheet [Member] | Other Commodity [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment:	2,962		3,286
Individually evaluated for impairment:	58		69
Total Farm & Ranch loans:	3,020		3,355
Allowance for Losses:
Collectively evaluated for impairment:	5		5
Individually evaluated for impairment:	0		1
Total Farm & Ranch loans:	$ 5		$ 6