Loans and Allowance for Losses - Schedule of Impaired Financing Receivables (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Financing Receivable, Impaired [Line Items]
Impaired Loans, With so specific allowance, Recorded investment	$ 49,001		$ 49,001		$ 32,012
Impaired Loans, With so specific allowance, Unpaid principal balance	48,813		48,813		31,854
Impaired Loan, With a specific allowance, Recorded investment	123,412		123,412		123,300
Impaired Loans, With a specific allowance, Unpaid principal balance	122,985		122,985		122,786
Impaired Loans, Associated allowance	3,845		3,845		3,405
Recorded investment	172,413		172,413		155,312
Unpaid principal balance	171,798		171,798		154,640
Recorded investment of loans on nonaccrual status	61,855		61,855		61,408
Average recorded investment in impaired loans	173,616	$ 155,019	162,168	$ 151,170
Income recognized on impaired loans	859	941	1,660	1,639
Crops [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, With so specific allowance, Recorded investment	25,163		25,163		20,734
Impaired Loans, With so specific allowance, Unpaid principal balance	25,067		25,067		20,632
Impaired Loan, With a specific allowance, Recorded investment	73,953		73,953		59,335
Impaired Loans, With a specific allowance, Unpaid principal balance	73,693		73,693		59,098
Impaired Loans, Associated allowance	2,344		2,344		1,606
Recorded investment	99,116		99,116		80,069
Unpaid principal balance	98,760		98,760		79,730
Recorded investment of loans on nonaccrual status	35,437		35,437		26,611
Average recorded investment in impaired loans	98,176	72,041	85,652	74,527
Income recognized on impaired loans	379	327	701	719
Permanent Plantings [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, With so specific allowance, Recorded investment	14,402		14,402		3,592
Impaired Loans, With so specific allowance, Unpaid principal balance	14,346		14,346		3,573
Impaired Loan, With a specific allowance, Recorded investment	24,489		24,489		38,176
Impaired Loans, With a specific allowance, Unpaid principal balance	24,401		24,401		38,009
Impaired Loans, Associated allowance	882		882		1,134
Recorded investment	38,891		38,891		41,768
Unpaid principal balance	38,747		38,747		41,582
Recorded investment of loans on nonaccrual status	12,778		12,778		21,349
Average recorded investment in impaired loans	39,056	49,919	41,903	45,945
Income recognized on impaired loans	121	492	420	664
Livestock [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, With so specific allowance, Recorded investment	7,475		7,475		5,764
Impaired Loans, With so specific allowance, Unpaid principal balance	7,447		7,447		5,737
Impaired Loan, With a specific allowance, Recorded investment	18,786		18,786		19,443
Impaired Loans, With a specific allowance, Unpaid principal balance	18,728		18,728		19,361
Impaired Loans, Associated allowance	495		495		522
Recorded investment	26,261		26,261		25,207
Unpaid principal balance	26,175		26,175		25,098
Recorded investment of loans on nonaccrual status	10,289		10,289		8,803
Average recorded investment in impaired loans	28,650	23,453	26,279	21,361
Income recognized on impaired loans	304	60	417	139
Part-Time Farm [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, With so specific allowance, Recorded investment	1,903		1,903		1,922
Impaired Loans, With so specific allowance, Unpaid principal balance	1,895		1,895		1,912
Impaired Loan, With a specific allowance, Recorded investment	6,184		6,184		6,276
Impaired Loans, With a specific allowance, Unpaid principal balance	6,163		6,163		6,249
Impaired Loans, Associated allowance	124		124		142
Recorded investment	8,087		8,087		8,198
Unpaid principal balance	8,058		8,058		8,161
Recorded investment of loans on nonaccrual status	3,351		3,351		4,645
Average recorded investment in impaired loans	7,675	9,214	8,268	8,780
Income recognized on impaired loans	55	62	122	117
Agriculture Storage and Processing [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, With so specific allowance, Recorded investment	0		0		0
Impaired Loans, With so specific allowance, Unpaid principal balance	0		0		0
Impaired Loan, With a specific allowance, Recorded investment	0		0		0
Impaired Loans, With a specific allowance, Unpaid principal balance	0		0		0
Impaired Loans, Associated allowance	0		0		0
Recorded investment	0		0		0
Unpaid principal balance	0		0		0
Recorded investment of loans on nonaccrual status	0		0		0
Average recorded investment in impaired loans	0	0	0	0
Income recognized on impaired loans	0	0	0	0
Other Commodity [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, With so specific allowance, Recorded investment	58		58		0
Impaired Loans, With so specific allowance, Unpaid principal balance	58		58		0
Impaired Loan, With a specific allowance, Recorded investment	0		0		70
Impaired Loans, With a specific allowance, Unpaid principal balance	0		0		69
Impaired Loans, Associated allowance	0		0		1
Recorded investment	58		58		70
Unpaid principal balance	58		58		69
Recorded investment of loans on nonaccrual status	0		0		0
Average recorded investment in impaired loans	59	392	66	557
Income recognized on impaired loans	0	$ 0	0	$ 0
Less than 90 days past due [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment of loans on nonaccrual status	41,000		41,000		41,800
Collateral Dependent Not Individually Analyzed [Member]
Financing Receivable, Impaired [Line Items]
Impaired Loans, Associated allowance	2,600		2,600		2,700
Recorded investment	$ 121,000		$ 121,000		$ 120,900
Impaired loans, impairment analysis performed percent	70.00%		70.00%		78.00%