Accounting Policies - Cash and Cash Equivalents and Statements of Cash Flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Non-cash activity:
SEC Schedule III, Real Estate, Acquisitions Through Foreclosures	$ 5,261	$ 0
Proceeds from sale of Farmer Mac Guaranteed Securities	404,246	457,369
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	277,307	402,841
Purchases of Investment Securities Traded, Not Yet Settled	$ 9,987	$ 25,000