Accounting Policies - Consolidation of Variable Interest Entities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	$ 708,111	$ 692,478
Debt securities of consolidated trusts held by third parties	713,536	424,214
Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Other Liabilities	5,400	2,900
USDA Guarantees [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	(200)	200
Rural Utilities [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)		3,700
Institutional Credit [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	1,400
Fair Value Adjustment		2,400
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	1,494,323	1,620,064
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	514,051	636,086
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	10,272	13,978
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
On-balance sheet [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	708,111	692,478
Debt securities of consolidated trusts held by third parties	713,536	424,214
On-balance sheet [Member] | Farm & Ranch [Member]
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	708,111	421,355
Debt securities of consolidated trusts held by third parties	713,536	424,214
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	271,123
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
Investment Securities [Member]
Variable Interest Entity [Line Items]
Unamortized Premium/(Discount)	5,936	7,471
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	917,292	409,657
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	918,121	412,690
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	917,292	409,657
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	918,121	412,690
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	62,760	60,035
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	61,553	57,832
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	31,360	27,620
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	31,553	27,832
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	31,400	32,415
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