Accounting Policies - Cash and Cash Equivalents and Statements of Cash Flows (Details) - USD ($) $ in Thousands		3 Months Ended						12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014		Oct. 01, 2016	Jan. 02, 2014
Other Significant Noncash Transactions [Line Items]
Transfer of USDA Guaranteed Securities- Available-for-sale to Held-to-maturity; Unrealized holding gains												$ 73,100
Transfer of Farmer Mac Guaranteed Securities - Available-for-sale to Held-to-maturity; Unrealized holding gains												700	$ 22,300
Transfer of Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Available-for-sale to Held-to-maturity; Unrealized holding gains												$ 73,800
Interest Paid								$ 110,609	$ 108,254	$ 171,644
Income Taxes Paid								29,500	31,000	12,750
Non-cash activity:
Proceeds from sale of Farmer Mac Guaranteed Securities								609,347	336,913	175,754
Consolidation of Farm & Ranch Guaranteed Securities from off-balance sheet to loans held for investment in consolidated trusts and to debt securities of consolidated trusts held by third parties								511,393	336,913	199,906
Purchases of securities - traded, not yet settled								0	20,000	70,178
Issuance Costs on the retirement of Farmer Mac II LLC Preferred Stock		$ 0	$ 0	$ 0	$ 8,147			0	8,147	0
Unsettled Class C Common Stock Repurchases								0	197	0
Institutional Credit [Member]
Non-cash activity:
Issuance Costs on the retirement of Farmer Mac II LLC Preferred Stock									0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Other Significant Noncash Transactions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3								2,013,151		1,632,786
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | USDA Securities [Member]
Other Significant Noncash Transactions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3								1,980,327		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available-for-sale Securities [Member] | USDA Securities [Member]
Other Significant Noncash Transactions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	[1]							1,980,327	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member]
Other Significant Noncash Transactions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3								32,824	$ 0	1,632,786
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Institutional Credit [Member] | Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member]
Other Significant Noncash Transactions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3						$ 0	$ 1,600,000	0		$ 1,632,786	[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Farmer Mac Guaranteed Securities [Member] | Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member]
Other Significant Noncash Transactions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3								32,800
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | USDA Guarantee [Member] | Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member]
Other Significant Noncash Transactions [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3								$ 2,000,000

[1] Includes $32.8 million of Farmer Mac Guaranteed USDA Securities and $2.0 billion of USDA Securities transferred from available-for-sale to held-to-maturity on October 1, 2016.

[2] Includes $1.6 billion of AgVantage securities transferred from available-for-sale to held-to-maturity on January 1, 2014 and $20.7 million of AgVantage securities purchased during 2014 transferred from available-for-sale to held-to-maturity.