Loans and Allowance for Losses and Concentrations of Credit Risk - Allowance for Credit Losses Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Allowance for Loan Losses	$ 4,480
Beginning Balance - Reserve for Losses	2,083
Beginning Balance - Total Allowance for Losses	6,563	$ 10,127
Provision for loan losses	(49)	(76)
Provision for/(release of) reserve for losses	14	(772)
Total (release of)/provision for losses	63	(696)
Ending Balance - Allowance for Loan Losses	4,529
Ending Balance - Reserve for Losses	2,097
Ending Balance - Total Allowance for Losses	6,626	9,431
Crops [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	2,791	2,519
Total (release of)/provision for losses	101	121
Ending Balance - Total Allowance for Losses	2,892	2,640
Permanent Plantings [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	931	2,159
Total (release of)/provision for losses	6	125
Ending Balance - Total Allowance for Losses	937	2,284
Livestock [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	1,781	1,423
Total (release of)/provision for losses	(18)	(80)
Ending Balance - Total Allowance for Losses	1,763	1,343
Part-Time Farm [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	408	467
Total (release of)/provision for losses	36	(8)
Ending Balance - Total Allowance for Losses	444	459
Agriculture Storage and Processing [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	649	3,552
Total (release of)/provision for losses	(62)	(854)
Ending Balance - Total Allowance for Losses	587	2,698
Other Commodity [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Total Allowance for Losses	3	7
Total (release of)/provision for losses	0	0
Ending Balance - Total Allowance for Losses	3	7
Allowance for Loan and Lease Losses [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Allowance for Loan Losses	4,480	5,864
Provision for loan losses	(49)	(76)
Financing Receivable, Allowance for Credit Losses, Write-downs	0	0
Ending Balance - Allowance for Loan Losses	4,529	5,940
Reserve for Off-balance Sheet Activities [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance - Reserve for Losses	2,083	4,263
Provision for/(release of) reserve for losses	14	(772)
Ending Balance - Reserve for Losses	$ 2,097	$ 3,491