FAIR VALUE DISCLOSURES - Schedule of Unobservable Input Reconciliation (Details) - Level 3 - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 7,781,421	$ 5,756,119	$ 6,744,017	$ 5,539,404
Purchases	0	350,000	1,540,320	750,000
Settlements	(30,260)	(249,764)	(458,813)	(543,124)
Allowance for Losses	6	60	57	104
Realized and unrealized (losses)/gains included in Income	$ (194,025)	$ 19,282	$ (252,397)	$ 139,090
Fair Value Recurring Basis Unobservable Input Reconciliation Asset Gain Loss Statement Of Income Extensible List Not Disclosed Flag	Realized andunrealized (losses)/gains included in Income	Realized andunrealized gains/(losses) included in Income	Realized andunrealized (losses)/gains included in Income	Realized andunrealized gains/(losses) included in Income
Unrealized (losses)/gains included in other comprehensive income	$ 10,007	$ 2,932	$ (6,035)	$ (6,845)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Net unrealized (losses)/gains on available-for-sale securities	Net unrealized (losses)/gains on available-for-sale securities	Net unrealized (losses)/gains on available-for-sale securities	Net unrealized (losses)/gains on available-for-sale securities
Ending Balance	$ 7,567,149	$ 5,878,629	$ 7,567,149	$ 5,878,629
Available-for-sale securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	7,776,569	5,750,978	6,739,120	5,534,022
Purchases	0	350,000	1,540,320	750,000
Settlements	(30,187)	(249,680)	(458,585)	(542,869)
Allowance for Losses	6	60	57	104
Realized and unrealized (losses)/gains included in Income	(193,929)	19,290	(252,411)	139,168
Unrealized (losses)/gains included in other comprehensive income	10,007	2,932	(6,035)	(6,845)
Ending Balance	7,562,466	5,873,580	7,562,466	5,873,580
ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	65,474
Purchases	0
Settlements	(4)
Allowance for Losses	0
Realized and unrealized (losses)/gains included in Income	(4,404)
Unrealized (losses)/gains included in other comprehensive income	(40)
Ending Balance	61,026		61,026
Auction-rate certificates backed by Government guaranteed student loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance		19,475	0	19,476
Purchases		0	65,320	0
Settlements		0	(5)	0
Allowance for Losses		7	0	6
Realized and unrealized (losses)/gains included in Income		0	(5,034)	0
Unrealized (losses)/gains included in other comprehensive income		0	745	0
Ending Balance		19,482		19,482
AgVantage
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	7,702,969	5,722,890	6,730,917	5,505,531
Purchases	0	350,000	1,475,000	750,000
Settlements	(30,045)	(249,516)	(458,142)	(542,365)
Allowance for Losses	6	53	57	98
Realized and unrealized (losses)/gains included in Income	(189,525)	19,290	(247,377)	139,168
Unrealized (losses)/gains included in other comprehensive income	10,192	2,925	(6,858)	(6,790)
Ending Balance	7,493,597	5,845,642	7,493,597	5,845,642
Interest-Only Farmer Mac Guaranteed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	8,126	8,613	8,203	9,015
Purchases	0	0	0	0
Settlements	(138)	(164)	(438)	(504)
Allowance for Losses	0	0	0	0
Realized and unrealized (losses)/gains included in Income	0	0	0	0
Unrealized (losses)/gains included in other comprehensive income	(145)	7	78	(55)
Ending Balance	7,843	8,456	7,843	8,456
Other Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4,852	5,141	4,897	5,382
Purchases	0	0	0	0
Settlements	(73)	(84)	(228)	(255)
Allowance for Losses	0	0	0	0
Realized and unrealized (losses)/gains included in Income	(96)	(8)	14	(78)
Unrealized (losses)/gains included in other comprehensive income	0	0	0	0
Ending Balance	$ 4,683	$ 5,049	$ 4,683	$ 5,049