Accounting Policies - Consolidation of Variable Interest Entities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	$ 1,132,966	$ 708,111
Debt securities of consolidated trusts held by third parties	1,142,704	713,536
Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Other Liabilities	9,700	5,400
USDA Guarantees [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	400	(200)
Institutional Credit [Member]
Variable Interest Entity [Line Items]
Fair Value Adjustment	300	1,400
On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	1,132,966	708,111
Debt securities of consolidated trusts held by third parties	1,142,704	713,536
On-balance sheet [Member] | Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	1,132,966	708,111
Debt securities of consolidated trusts held by third parties	1,142,704	713,536
On-balance sheet [Member] | USDA Guarantees [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	0	0
Debt securities of consolidated trusts held by third parties	0	0
On-balance sheet [Member] | Rural Utilities [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	0	0
Debt securities of consolidated trusts held by third parties	0	0
On-balance sheet [Member] | Institutional Credit [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	0	0
Debt securities of consolidated trusts held by third parties	0	0
On-balance sheet [Member] | Corporate Segment [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	0	0
Debt securities of consolidated trusts held by third parties	0	0
Off-balance sheet [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	1,489,417	1,494,323
Off-balance sheet [Member] | Farm & Ranch [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	415,441	514,051
Off-balance sheet [Member] | USDA Guarantees [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	103,976	10,272
Off-balance sheet [Member] | Rural Utilities [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Off-balance sheet [Member] | Institutional Credit [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	970,000	970,000
Off-balance sheet [Member] | Corporate Segment [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	66,389	62,760
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	65,599	61,553
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Farm & Ranch [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | USDA Guarantees [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	36,042	31,360
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	35,599	31,553
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Rural Utilities [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Institutional Credit [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	30,347	31,400
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	30,000	30,000
Farmer Mac Guaranteed Securities: | On-balance sheet [Member] | Corporate Segment [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Investment Securities [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	5,672	5,936
Investment Securities [Member] | On-balance sheet [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	827,874	917,292
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	825,909	918,121
Investment Securities [Member] | On-balance sheet [Member] | Farm & Ranch [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Investment Securities [Member] | On-balance sheet [Member] | USDA Guarantees [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Investment Securities [Member] | On-balance sheet [Member] | Rural Utilities [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Investment Securities [Member] | On-balance sheet [Member] | Institutional Credit [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	0	0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0	0
Investment Securities [Member] | On-balance sheet [Member] | Corporate Segment [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net	827,874	917,292
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 825,909	$ 918,121