SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Consolidation of Variable Interest Entities (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	$ 13,192,117	$ 11,183,408
Debt securities of consolidated trusts held by third parties	29,204,490	27,520,173
Farmer Mac Guaranteed USDA Securities
Variable Interest Entity [Line Items]
Guarantee and commitment obligation	$ 5,100	$ 5,600
Weighted-average remaining maturity	20 years 10 months 24 days	21 years 2 months 12 days
Farmer Mac Guaranteed Securities
Variable Interest Entity [Line Items]
Carrying value	$ 5,854,098	$ 5,514,546
Investment securities
Variable Interest Entity [Line Items]
Carrying value	6,655,946	5,953,014
Agricultural Finance
Variable Interest Entity [Line Items]
Borrower remittances	1,400	4,700
Unamortized discount	117,500	113,200
Consolidated VIE | On-balance sheet
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	2,205,213	2,038,283
Debt securities of consolidated trusts held by third parties	2,089,042	1,929,628
Consolidated VIE | Operating Segments | On-balance sheet | Agricultural Finance
Variable Interest Entity [Line Items]
Loans held for investment in consolidated trusts, at amortized cost	2,205,213	2,038,283
Debt securities of consolidated trusts held by third parties	2,089,042	1,929,628
Consolidated VIE | Operating Segments | On-balance sheet | Treasury
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
Unconsolidated VIE | On-balance sheet | Farmer Mac Guaranteed Securities
Variable Interest Entity [Line Items]
Carrying value	79,302	59,317
Maximum exposure to loss	79,027	58,985
Unconsolidated VIE | On-balance sheet | Investment securities
Variable Interest Entity [Line Items]
Carrying value	4,769,276	4,212,258
Maximum exposure to loss	4,959,042	4,547,397
Unconsolidated VIE | Off-balance sheet
Variable Interest Entity [Line Items]
Maximum exposure to loss	392,358	426,310
Unconsolidated VIE | Operating Segments | On-balance sheet | Agricultural Finance | Farmer Mac Guaranteed Securities
Variable Interest Entity [Line Items]
Carrying value	79,302	59,317
Maximum exposure to loss	79,027	58,985
Unconsolidated VIE | Operating Segments | On-balance sheet | Agricultural Finance | Investment securities
Variable Interest Entity [Line Items]
Carrying value	0	0
Maximum exposure to loss	0	0
Unconsolidated VIE | Operating Segments | On-balance sheet | Treasury | Farmer Mac Guaranteed Securities
Variable Interest Entity [Line Items]
Carrying value	0	0
Maximum exposure to loss	0	0
Unconsolidated VIE | Operating Segments | On-balance sheet | Treasury | Investment securities
Variable Interest Entity [Line Items]
Carrying value	4,769,276	4,212,258
Maximum exposure to loss	4,959,042	4,547,397
Unconsolidated VIE | Operating Segments | Off-balance sheet | Agricultural Finance
Variable Interest Entity [Line Items]
Maximum exposure to loss	392,358	426,310
Unconsolidated VIE | Operating Segments | Off-balance sheet | Treasury
Variable Interest Entity [Line Items]
Maximum exposure to loss	$ 0	$ 0