Derivative Instruments and Hedging Activities - Derivatives - Schedule of notional amounts of derivative instruments having rating triggers (Details) - USD ($) $ in Thousands	May 31, 2026	May 31, 2025
Interest rate swap rating trigger
Derivative [Line Items]
Notional Amount	$ 4,692,652
Payable Due from CFC	(941)
Receivable Due to CFC	365,181
Net Receivable (Payable)	364,240
Interest rate swaps
Derivative [Line Items]
Notional Amount	6,565,533	$ 7,252,235
Falls below A3/A- | Interest rate swap rating trigger
Derivative [Line Items]
Notional Amount	14,000
Payable Due from CFC	(353)
Receivable Due to CFC	0
Net Receivable (Payable)	(353)
Falls below Baa1/BBB+ | Interest rate swap rating trigger
Derivative [Line Items]
Notional Amount	3,315,616
Payable Due from CFC	(588)
Receivable Due to CFC	258,627
Net Receivable (Payable)	258,039
Falls to or below Baa2/BBB | Interest rate swap rating trigger
Derivative [Line Items]
Notional Amount	436,761
Payable Due from CFC	0
Receivable Due to CFC	22,332
Net Receivable (Payable)	22,332
Falls below Baa2/BBB | Interest rate swaps | Counterparty Group | Minimum
Derivative [Line Items]
Notional Amount	926,275
Payable Due from CFC	0
Receivable Due to CFC	84,222
Net Receivable (Payable)	$ 84,222