Accounting Policies - Cash and Cash Equivalents and Statements of Cash Flows (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Non-cash activity:
SEC Schedule III, Real Estate, Acquisitions Through Foreclosures	$ 5,261	$ 0
Proceeds from sale of Farmer Mac Guaranteed Securities	247,975	278,443
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	161,880	255,781
Purchases of Investment Securities Traded, Not Yet Settled	$ 50,000	$ 224,990